Layer forming method, product comprising the layer, optical film, dielectric-coated electrode and plasma discharge apparatus

ABSTRACT

A layer forming method is disclosed which comprises the steps of supplying power of not less than 1 W/cm 2  at a high frequency voltage exceeding 100 kHz across a gap between a first electrode and a second electrode opposed to each other at atmospheric pressure or at approximately atmospheric pressure to induce a discharge, generating a reactive gas in a plasma state by the charge, and exposing a substrate to the reactive gas in a plasma state to form a layer on the substrate.

FIELD OF THE INVENTION

The present invention relates to a method of forming various function oflayers having high quality, a product with the layer, an optical filmwith the layer which is an anti-reflection layer, a dielectric coatedelectrode suitable for forming the layer, and a plasma dischargeapparatus comprising the dielectric coated electrode, and particularlyto a method of forming a layer on a substrate comprising generating areactive gas in a plasma state at atmospheric pressure or approximatelyatmospheric pressure and exposing the substrate to the reactive gas in aplasma state to form a layer on the substrate, a product with the layer,an optical film, a dielectric coated electrode, and a plasma dischargeapparatus.

BACKGROUND OF THE INVENTION

Many materials in which a layer with high function is provided on asubstrate are used in various kinds of products, for example, an LSI, asemi-conductor, a displaying device, a magnetic recording device, lightto electricity conversion device, a Josephson device, a solar battery,and a light heat conversion device. Examples of the layer with highfunction include an electrode layer, a dielectric protective layer, asemi-conductor layer, a transparent electro-conductive layer, anelectrochromic layer, a fluorescent layer, a superconduction layer, adielectric layer, a solar battery layer, an anti-reflection layer, ananti-abrasion layer, an optical interference layer, a reflection layer,an anti-static layer, an electroconductive layer, an anti-stain layer, ahard coat layer, a subbing layer, a barrier layer, an electromagneticradiation shielding layer, an infrared ray shielding layer, a UVabsorption layer, a lubricant layer, a shape-memory layer, a magneticrecording layer, a light emission element layer, a layer applied toorganisms, an anti-corrosion layer, a catalyst layer, a gas-sensorlayer, and a layer for decoration. These layers with high function areformed according to a wet coating method such as a solution coatingmethod or according to a dry coating method employing vacuum processingsuch as a spattering method, a vacuum evaporation method or an ionplating method.

The solution coating method is advantageous in high productivity, but isnot necessarily suitable for formation of a layer with high function,since it is necessary to dissolve or disperse materials constituting thelayer in a solvent to prepare a coating solution, and when the coatingsolution is coated on a substrate to form a layer, the solvent usedremains in the resulting layer or it is difficult to obtain a layer witha uniform thickness. The solution coating method further has problem inthat at the drying process after coating, the solvent evaporated fromthe coating solution pollutes environment.

On the other hand, the dry coating method employing vacuum processingcan provide a layer with high precision and is preferable in forming alayer with high function. However, the dry coating method, when asubstrate to be processed is of large size, requires a large-scalevacuum processing apparatus, which is too expensive and time-consumingfor evacuation, resulting in disadvantage of lowering of productivity.As a method for overcoming the demerits in that the solution coatingmethod is difficult to provide a layer with high function or use of avacuum processing apparatus results in lowering of productivity, amethod is described in Japanese Patent O.P.I. Publication Nos.11-133205, 2000-185362, 11-61406, 2000-147209, and 2000-121804, whichcomprises subjecting a reactive gas to discharge treatment atatmospheric pressure or approximately atmospheric pressure, exciting thereactive gas to a plasma state and forming a layer on a substrate(hereinafter referred to also as an atmospheric pressure plasma method).The atmospheric pressure plasma method disclosed in these publicationsgenerates discharge plasma between two opposed electrodes by applyingpulsed electric field with a frequency of from 0.5 to 100 kHz and with astrength of electric field of from 1 to 100 V/cm. However, although alayer with high function can be formed in only a small area according tothe atmospheric pressure plasma method disclosed in the aforementionedpublications, it is difficult to form a uniform layer over a large area.Further, it has been proved that the layer formed does not sufficientlysatisfy performance to be required for a layer with high function.Accordingly, a means for solving these problems occurring in the layerformation as described above has been required.

The present invention has been made in view of the above. An object ofthe invention is to provide a method of uniformly forming a layer withhigh function over a large area with high productivity and with highproduction efficiency, a product comprising the layer, and an opticalfilm comprising the layer, and to provide a dielectric coated electrodeand a plasma discharge apparatus for carrying out the method andobtaining the product and the optical film.

DISCLOSURE OF THE INVENTION

The above object of the invention can be attained by each of thefollowing constitutions:

(1) A layer forming method comprising the steps of supplying power ofnot less than 1 W/cm² at a high frequency voltage exceeding 100 kHzacross a gap between opposed electrodes at atmospheric pressure or atapproximately atmospheric pressure to induce a discharge, generating areactive gas in a plasma state by the charge, and exposing a substrateto the reactive gas in a plasma state to form a layer on the substrate.

(2) The layer forming method as described in item (1), wherein the totalpower supplied to the electrode exceeds 15 kW.

(3) The layer forming method as described in item (1) or (2), whereinthe high frequency voltage has a continuous sine-shaped wave.

(4) The layer forming method as described in any one of items (1)through (3), wherein the substrate is relatively transported to at leastone of the electrodes, whereby the layer is formed on the substrate.

(5) The layer forming method as described in any one of items (1)through (4), wherein the substrate is placed between the electrodes, andthe reactive gas is introduced to the gap between the electrodes,whereby the layer is formed on the substrate.

(6) The layer forming method as described in item (4) or (5), whereinthe length in the transverse direction of a discharge surface of theelectrodes is equal to or greater than that in transverse direction ofthe substrate on which a layer is to be formed, the transverse directionbeing perpendicular to the transport direction.

(7) The layer forming method as described in item (6) wherein the lengthin the transport direction of a discharge surface of the electrode isnot less than one tenth the length in the transverse direction of adischarge surface of the electrode.

(8) The layer forming method as described in item (7), wherein thedischarge surface area of the electrode is not less than 1000 cm².

(9) The layer forming method as described in any one of items (1)through (8), wherein at least one on one side of the electrodes is adielectric coated electrode whose discharge surface is coated with adielectric to form a dielectric layer.

(10) The layer forming method as described in item (9), wherein thedielectric layer is one formed by thermally spraying ceramic to form aceramic layer and sealing the ceramic layer with an inorganic compound.

(11) The layer forming method as described in item (10), wherein theceramic is alumina.

(12) The layer forming method as described in item (10) or (11), whereinthe inorganic compound for the sealing is hardened by a sol-gelreaction.

(13) The layer forming method as described in item (12), wherein thesol-gel reaction is accelerated by energy treatment.

(14) The layer forming method as described in item (13), wherein theenergy treatment is heat treatment at not more than 200° C. or UVirradiation treatment.

(15) The layer forming method as described in any one of items (12)through (14), wherein the inorganic compound for the sealing after thesol-gel reaction contains not less than 60 mol % of SiO_(x).

(16) The layer forming method as described in any one of items (9)through (15), wherein the dielectric layer has a void volume of not morethan 10% by volume.

(17) The layer forming method as described in item (16), wherein thedielectric layer has a void volume of not more than 8% by volume.

(18) The layer forming method as described in any one of items (9)through (17), wherein the dielectric coated electrode has a heatresistant temperature of not less than 100° C.

(19) The layer forming method as described in any one of items (9)through (18), wherein the dielectric coated electrode has the dielectriclayer on a conductive base material, and the difference in a linearthermal expansion coefficient between the conductive base material andthe dielectric is not more than 10×10⁻⁶/° C.

(20) The layer forming method as described in any one of items (9)through (19), wherein the dielectric has a dielectric constant of from 6to 45.

(21) The layer forming method as described in any one of items (1)through (20), wherein at least one electrode on one side of theelectrodes has a cooling means comprising a path for chilled water inthe interior, the at least one electrode being cooled by supplyingchilled water to the path.

(22) The layer forming method as described in any one of items (1)through (21), wherein the substrate is a long-length film, at least oneelectrode on one side of the opposed electrodes is a roll electrode,which contacts the film and is rotated in the transport direction of thefilm, and the other electrode being opposed to the roll electrode is anelectrode group comprising plural electrodes.

(23) The layer forming method as described in item (22), wherein each ofthe plural electrodes is prismatic.

(24) The layer forming method as described in item (22) or (23), whereinthe surface on the side contacting the substrate of the roll electrodeis subjected to polishing treatment.

(25) The layer forming method as described in item (24), wherein thesurface on the side contacting the substrate of the roll electrode has asurface roughness Rmax of not more than 10 μm.

(26) The layer forming method as described in any one of items (22)through (25), wherein air, which is introduced to the gap between theopposed electrodes together with the long-length film transported to thegap, is less than 1% by volume.

(27) The layer forming method as described in any one of items (22)through (26), wherein at least one power source is coupled between theone roll electrode and the electrode group, and the power source iscapable of supplying a total power of not less than 15 kW.

(28) The layer forming method as described in any one of items (1)through (27), wherein a mixed gas containing an inert gas and thereactive gas is introduced to a gap between the electrodes and the mixedgas contains 90 to 99.9% by volume of the inert gas.

(29) The layer forming method as described in item (28), wherein themixed gas contains not less than 90% by volume of an argon gas.

(30) The layer forming method as described in item (28) or (29), whereinthe mixed gas contains 0.01 to 5% by volume of a component selected fromoxygen, ozone, hydrogen peroxide, carbon dioxide, carbon monoxide,hydrogen and nitrogen.

(31) The layer forming method as described in any one of items (1)through (30), wherein the reactive gas contains a component selectedfrom an organometallic compound and an organic compound.

(32) The layer forming method as described in item (31), wherein theorganometallic compound comprises a metal selected from Li, Be, B, Na,Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Rb,Sr, Y, Zr, Nb, Mo, Cd, In, Ir, Sn, Sb, Cs, Ba, La, Hf, Ta, W, Tl, Bi,Ce, Pr, Nd, Pm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

(33) The layer forming method as described in item (32), wherein theorganometallic compound is one selected from a metal alkoxide, analkylated metal, and a metal complex.

(34) The layer forming method as described in any one of items (1)through (33), wherein the layer contains a compound selected from ametal, a metal oxide, a metal nitride, a metal carbide, and a metalboride.

(35) The layer forming method as described in item (34), wherein thelayer contains a compound selected from a metal, a metal oxide, a metalnitride, and a metal boride.

(36) The layer forming method as described in item (35), wherein thelayer contains a metal oxide.

(37) The layer forming method as described in item (35) or (36), whereinthe layer has a carbon content of from 0.1 to 5% by weight.

(38) The layer forming method as described in item (37), wherein thelayer has a carbon content of from 0.2 to 5% by weight.

(39) The layer forming method as described in item (38), wherein thelayer has a carbon content of from 0.3 to 3% by weight.

(40) The layer forming method as described in any one of items (1)through (39), wherein the layer has a thickness of from 0.1 to 1000 nm.

(41) The layer forming method as described in any one of items (1)through (40), wherein the layer is one selected from an electrode layer,a dielectric protective layer, a semi-conductor layer, a transparentelectro-conductive layer, an electro-chromic layer, a fluorescent layer,a superconduction layer, a dielectric layer, a solar battery layer, ananti-reflection layer, an anti-abrasion layer, an optical interferencelayer, a reflection layer, an anti-static layer, an electroconductivelayer, an anti-stain layer, a hard coat layer, a subbing layer, abarrier layer, an electromagnetic radiation shielding layer, an infraredray shielding layer, a UV absorption layer, a lubricant layer, ashape-memory layer, a magnetic recording layer, a light emission elementlayer, a layer applied to organisms, an anti-corrosion layer, a catalystlayer, a gas-sensor layer, and a layer for decoration.

(42) The layer forming method as described in item (41), wherein thelayer is an anti-reflection layer.

(43) The layer forming method as described in item (20), wherein thesubstrate contains cellulose ester as a material.

(44) A product having on a substrate a layer formed according to thelayer forming method as described in any one of items (1) through (43).

(45) The product as described in item (44), which is an optical filmhaving an anti-reflection layer.

(46) The product as described in item (45), wherein the anti-reflectionlayer comprises a high refractive index layer with a refractive index of1.6 to 2.4 containing titanium oxide as a main component and a lowrefractive index layer with a refractive index of 1.3 to 1.5 containingsilicon oxide as a main component.

(47) The product as described in item (46), wherein the refractive indexof the high refractive index layer is not less than 2.2.

(48) A product having on a substrate a layer containing a metal oxide asa main component, wherein the metal oxide layer has a carbon content offrom 0.1 to 5% by weight.

(49) The product as described in item (48), wherein the metal oxidelayer has a carbon content of from 0.2 to 5% by weight.

(50) The product as described in item (49), wherein the metal oxidelayer has a carbon content of from 0.3 to 3% by weight.

(51) The product as described in any one of items (48) through (50),wherein the metal oxide is titanium oxide.

(52) The product as described in item (51), wherein the layer containingtitanium oxide as a main component has a refractive index of not lessthan 2.2.

(53) The product as described in any one of items (48) through (52),wherein the metal oxide is silicon oxide

(54) An optical film having on a substrate an anti-reflection layer,wherein the anti-reflection layer comprises a high refractive indexlayer with a refractive index of not less than 2.2, and the highrefractive index layer contains titanium oxide as a main component andhas a carbon content of from 0.1 to 5% by weight.

(55) The optical film as described in item (54), wherein the highrefractive index layer has a carbon content of from 0.2 to 5% by weight.

(56) The optical film as described in item (55), wherein the highrefractive index layer has a carbon content of from 0.3 to 3% by weight.

(57) The optical film as described in any one of items (54) through(56), wherein the anti-reflection layer further comprises a lowrefractive index layer with a refractive index of from 1.3 to 1.5containing silicon oxide as a main component.

(58) The optical film as described in any one of items (54) through(57), wherein the substrate contains cellulose ester.

(59) The optical film as described in item (58), wherein the substratecontains a plasticizer.

(60) The optical film as described in item (58) or (59), wherein thesubstrate has a clear hard coat layer or an anti-glare layer on itssurface.

(61) A dielectric coated electrode, in which a conductive base materialis coated with a dielectric to form a dielectric layer, wherein thedielectric layer has a void volume of not more than 10% by volume.

(62) The dielectric coated electrode as described in item (61), in whicha conductive base material is coated with a dielectric to form adielectric layer, wherein the dielectric layer has a void volume of notmore than 8% by volume.

(63) The dielectric coated electrode as described in item (61) or (62),wherein the electrode has a heat resistant temperature of not less than100° C.

(64) The dielectric coated electrode as described in any one of items(61) through (63), wherein the difference in a linear thermal expansioncoefficient between the conductive base material and the dielectriclayer in the dielectric coated electrode is not more than 10×10⁻⁶/° C.

(65) The dielectric coated electrode as described in any one of items(61) through (64), wherein the dielectric layer has a thickness of from0.5 to 2 mm.

(66) The dielectric coated electrode as described in any one of items(61) through (65), wherein the dielectric is an inorganic compoundhaving a dielectric constant of from 6 to 45.

(67) The dielectric coated electrode as described in any one of items(61) through (66), wherein the dielectric layer is one formed bythermally spraying ceramic on the conductive base material to form aceramic layer, and sealing the ceramic layer with an inorganic compound.

(68) The dielectric coated electrode as described in item (67) whereinthe ceramic comprises alumina as a main component.

(69) The dielectric coated electrode as described in item (67) or (68),wherein the inorganic compound for the sealing is hardened by a sol-gelreaction.

(70) The dielectric coated electrode as described in item (69), whereinthe sol-gel reaction is accelerated by energy treatment.

(71) The dielectric coated electrode as described in item (70), whereinthe energy treatment is heat treatment at not more than 200° C. or UVradiation treatment.

(72) The dielectric coated electrode as described in any one of items(69) through (71), wherein the inorganic compound for the sealing afterthe sol-gel reaction contains not less than 60 mol % of SiO_(x).

(73) The dielectric coated electrode as described in any one of items(61) through (72), wherein the surface of the dielectric layer issurface finished by polishing treatment.

(74) The dielectric coated electrode as described in item (73), whereinthe surface of the dielectric layer has a surface roughness Rmax of notmore than 10 μm.

(75) The dielectric coated electrode as described in any one of items(61) through (74), wherein the electrode has a cooling means comprisinga path for chilled water in the interior of the conductive basematerial, the electrode being cooled by supplying chilled water to thepath.

(76) The dielectric coated electrode as described in any one of items(61) through (75), wherein the electrode is prismatic.

(77) A plasma discharge apparatus providing a substrate at a gap betweenopposed electrodes, applying voltage across the gap at atmosphericpressure or approximately atmospheric pressure to induce a discharge,generating a reactive gas in a plasma state by the charge, and thenexposing the substrate to the reactive gas in a plasma state to form alayer on the substrate, wherein the electrode on at least one side ofthe opposed electrodes is the dielectric coated electrode as describedin any one of items (61) through (76).

(78) The plasma discharge apparatus as described in item (77), whereinthe substrate is a long-length film, the electrode on at least one sideof the opposed electrodes is one roll electrode, which contacts thelong-length film and is rotated in the transport direction of thelong-length film, and the other electrode opposed to the one rollelectrode is an electrode group comprising two or more of the dielectriccoated electrode.

(79) The plasma discharge apparatus as described in item (78), whereinthe roll electrode is the dielectric coated electrode.

(80) The plasma discharge apparatus as described in item (78) or (79),wherein the surface contacting the film of the roll electrode has asurface roughness Rmax of not more than 10 um. (81) The plasma dischargeapparatus as described in any one of items (77) through (80), whereinthe discharge surface area of the electrode is not less than 1000 cm².

(82) The plasma discharge apparatus as described in any one of items(77) through (81), wherein the length of the electrode is greater thanthat of the substrate.

(83) The plasma discharge apparatus as described in any one of items(77) through (81), wherein at least one power source is coupled betweenthe one roll electrode and the electrode group, and the power source iscapable of supplying a total power of not less than 15 kW.

(84) A plasma discharge apparatus providing a substrate at a gap betweenopposed electrodes, applying voltage across the gap at atmosphericpressure or approximately atmospheric pressure to induce a discharge,generating a reactive gas in a plasma state by the charge, and thenexposing the substrate to the reactive gas in a plasma state to form alayer on the substrate, wherein the substrate is a long-length film, theelectrode on at least one side of the opposed electrodes is a rollelectrode, which contacts the long-length film and is rotated in thetransport direction of the long-length film, the other electrode opposedto the roll electrode is a dielectric coated electrode, in which adielectric is coated on a conductive base material to form a dielectriclayer, and the surface contacting the film of the roll electrode has asurface roughness Rmax of not more than 10 μm.

(85) The plasma discharge apparatus as described in item (84), whereinthe surface contacting the film of the roll electrode is subjected topolishing treatment.

(86) A plasma discharge apparatus comprising the dielectric coatedelectrode as described in any one of items (61) through (76).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows one embodiment of a plasma discharge vessel provided in aplasma discharge apparatus used in the manufacturing method in theinvention.

FIG. 2 shows another embodiment of a plasma discharge vessel provided ina plasma discharge apparatus used in the manufacturing method of theinvention.

FIG. 3 shows one embodiment of a cylindrical roll electrode used forplasma discharge in the invention.

FIG. 4 shows one embodiment of a fixed, cylindrical electrode used forplasma discharge in the invention.

FIG. 5 shows one embodiment of a fixed, prismatic electrode used forplasma discharge in the invention.

FIG. 6 shows one embodiment of a plasma discharge apparatus used in thelayer forming method of the invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be detailed below.

The layer forming method of the invention comprises supplying power(output density) of not less than 1 W/cm² at a high frequency voltageexceeding 100 kHz across a gap between opposed electrodes, and excitinga reactive gas to generate plasma. In the invention, the upper limit ofthe frequency of the high frequency voltage applied across a gap betweenopposed electrodes is preferably not more than 150 MHz. The lower limitof the frequency of the high frequency voltage is preferably not lessthan 200 kHz, and more preferably not less than 800 kHz. The lower limitof power supplied across a gap between opposed electrodes is preferablynot less than 1.2 W/cm², and the upper limit of power supplied across agap between opposed electrodes is preferably not more than 50 W/cm², andmore preferably not more than 20 W/cm². The discharge surface area (cm²)refers to the surface area of the electrode at which discharge occurs.When a high voltage is applied at a high frequency and at a high outputdensity as in the invention, the discharge surface area corresponds tothe total area of the discharge surface of electrode arranged on oneside. The output density is obtained by dividing the total powersupplied from a power source coupled to the electrodes with the totalarea above.

In the invention, in order to form a layer with a uniform thickness overa large area, the total power supplied to a set of opposed electrodes ispreferably more than 15 kW, more preferably not less than 30 kW, andmost preferably not less than 50 kW. The total power is preferably notmore than 300 kW, in view of heat generation. The total power hereinreferred to corresponds to power supplied from a power source coupled tothe set of the opposed electrodes. When two or more power sources arecoupled to the electrode set above, the total power is the sum of powersupplied from each of the power sources. For example, in the plasmadischarge apparatus in FIG. 6 described later, the total power is apower supplied from power source 41 which is coupled to a set of opposedelectrodes composed of roll electrode 25 and prismatic electrodes 36. InFIG. 6, when the surfaces of the prismatic electrodes 36, facing theroll electrode 25, are discharge surfaces of voltage applicationelectrodes, the discharge surface area is the sum of the areas of thedischarge surfaces. When electrodes are cylindrical as electrodes 26shown in FIG. 1, the discharge surface area is the sum of the projectedareas of the cylindrical electrodes 26 onto the roll electrode 36.

In order to satisfy the total power range in the invention, it isnecessary that the discharge surface area is relatively large. The highfrequency voltage applied to the electrodes may be a continuous sinewave or a discontinuous pulsed wave. The continuous sine wave ispreferred in securing the effects of the invention. It is advantageousin attaining the object of the invention of forming a uniform layer withhigh density and without unevenness that the electrode is arranged sothat the discharge surface of the electrode faces the substrate surfaceon which the layer is to be formed. Accordingly, the substrate ispreferably provided between the electrodes.

It is preferred in forming a uniform layer with high performance andwithout unevenness that the length in at least one direction of theelectrode discharge surface is equal to or greater than that in thedirection of the substrate surface on which the layer is to be formed,the direction being the same as the electrode discharge surface. When asubstrate is transported relatively to the electrode to form a layer onthe substrate, it is preferred that in the direction perpendicular tothe transport direction of the substrate, the length of the electrodedischarge surface is equal to or greater than that of the substratesurface on which the layer is to be formed. Thus, according to themethod in which. the substrate is transported relatively to theelectrode to form a layer on the substrate, it is possible to form alayer over a large area at high speed simply by moving the substrate orthe electrode in one direction. The above means that, for example in theplasma discharge apparatus of FIG. 6, the length in the transversedirection (the direction perpendicular to the paper surface plane) ofthe discharge surface of the roll electrode 25 and the prismaticelectrodes 36 is equal to or greater than that of the substrate F. InFIG. 6, the length of roll electrode 25 and the prismatic electrodes 36is equal to that of the substrate F. When a layer is formed on asubstrate being transported relatively to the electrode in the layerforming method of the invention, the length in the transport directionof the electrode discharge surface is preferably not less than onetenth, more preferably not less than one fifth, and still morepreferably not less than one-half of the length in the transversedirection of the electrode discharge surface. This means that the longerlength in the transport direction of the electrode discharge surface ispreferred, whereby a layer having a uniform thickness with highperformance and without unevenness is formed. The longer length in thetransport direction of the electrode discharge surface increases thedischarge surface area, resulting in an increase of total power.

For example, in manufacturing an anti-reflection film employing a 100 cmwide long-length film as a substrate, a layer is formed whiletransporting the long-length film. In this example, when the length inthe transverse direction of the electrode discharge surface, thedirection being perpendicular to the film transport direction, is 100cm, the length in the transport direction of the electrode dischargesurface is not less than 10 cm, preferably not less than 12.5 cm andstill more preferably not less than 30 cm. It is preferred that thedischarge surface faces the substrate surface on which the layer is tobe formed. In view of the above, the area of the discharge surface ofthe electrode is preferably not less than 1000 cm², more preferably notless than 1300 cm², still more preferably not less than 1800 cm², andmost preferably not less than 3000 cm².

The present inventors have found that a layer with high density, with auniform thickness, with high performance and without unevenness can beobtained with high production efficiency applying a high power electricfield to a large area as described above. The present inventors assumethat the excellent effects result from the fact that plasma with highdensity can be uniformly generated over a large area according to thedischarge method as described above.

It is necessary in the invention that a plasma discharge apparatus beinstalled with electrodes with high durability which are capable ofmaintaining uniform discharge even when such a high electric field isapplied to a large surface area of the electrodes at atmosphericpressure or at approximately atmospheric pressure. Such electrodes arepreferably those in which a dielectric is coated on at least thedischarge surface of the surfaces of conductive base materials such asmetals. A dielectric is coated on at least one of a voltage applicationelectrode and a grounding electrode opposed to each other, andpreferably on both electrodes.

The dielectric coated electrode is a composite material comprised ofconductive base material such as metals and a dielectric such as ceramicor glass. When supplied power, particularly total supplied power, ishigh, the dielectric coated electrode is likely to be damaged at weakportions of the dielectric coat, making it difficult to maintain stableplasma discharge. This phenomenon is particularly marked in a dielectriccoated electrode with a large discharge surface, and accordingly inorder to carry out a layer forming method employing high power as in theinvention, a dielectric coated electrode capable of resisting such ahigh power is required.

The dielectric used in the dielectric coated electrode of the inventionis preferably an inorganic compound having a dielectric constant of from6 to 45. Examples thereof include ceramic such as alumina or siliconnitride, and a glass lining material such as silicate glass or borateglass. Of these, a dielectric layer is coated on the electrodepreferably by thermal spraying of ceramic or by glass-lining, and morepreferably by thermal spraying of alumina.

The present inventors have made an extensive study on dielectric coatedelectrodes, and have found a dielectric coated electrode coated with adielectric layer having a void volume of not more than 10% by volume,preferably not more than 8% by volume as one embodiment of theelectrodes as described above capable of resisting a high electricpower. A dielectric layer having a void volume of from more than 0 to 5%by volume is still more preferred. Herein, the void volume of thedielectric layer refers to a volume of voids having openings at thedielectric layer surface in the layer thickness direction, and can bemeasured employing a mercury porosimeter. In the examples describedlater, the void volume of a dielectric layer coated on a conductive basematerial was measured employing a Mercury Porosimeter produced byShimazu Seisakusho Co., Ltd. The dielectric layer having a low voidvolume provided high durability. A dielectric layer having voids whosevolume is low is, for example, a thermally sprayed ceramic layer withhigh density and high adhesion prepared according to an atmosphericplasma method as described later. In order to further reduce the voidvolume, a sealing treatment is preferably carried out.

Another preferred embodiment of the electrodes is a dielectric coatedelectrode in which a dielectric layer is coated on an electrode by meansof a glass lining method employing a glass produced according to amelting method. In this embodiment, a dielectric layer comprised of twoor more layers, which differ in foam content, provides higherdurability. It is preferred in the embodiment that the foam content ofthe lowest layer which contacts the conductive base material is 20 to30% by volume, and the foam content of the layer or layers provided onthe lowest layer is not more than 5% by volume. The foam content can becalculated from the density of glass itself and the density of the glasslining layer. The melted glass ordinarily foams but can be defoamed.Accordingly, the foam content can be adjusted to an intended valuevarying a defoaming degree. The dielectric formed in a layer accordingto a glass lining method, the foam content of which is controlled,provides an electrode with high durability. In the above embodiment itis preferred that the total thickness of the dielectric layers is 0.5 to2.0 mm, or the thickness of the lowest layer is not less than 0.1 mm,and the total thickness of the layer or layers provided on the lowestlayer is not less than 0.3 mm.

Still another preferred embodiment of the dielectric coated electrodesof the invention capable of resisting high electric power is one havinga heat resistant temperature of not less than 100° C., preferably notless than 120° C., and more preferably not less than 150° C. The heatresistant temperature herein refers to a highest temperature capable ofcarrying out normal discharge without causing dielectric breakdown. Theabove heat resistant temperature can be attained by employing adielectric layer. formed according to the thermal spray of ceramic asdescribed above, by employing a dielectric layer comprised of two ormore layers, which differ in foam content, formed according to theglass-lining as described above, or by properly selecting conductivebase materials and dielectrics in which the difference in linear thermalexpansion coefficient between the conductive base materials anddielectrics falls within the range as described below.

Still further another preferred embodiment of the dielectric coatedelectrodes of the invention is a combination of conductive base materialand dielectrics in which the difference in linear thermal expansioncoefficient between the conductive base material and dielectrics is notmore than 10×10⁻⁶/° C. The difference in linear thermal expansioncoefficient between the conductive base materials and dielectrics ispreferably not more than 8×10⁻⁶/° C., more preferably not more than5×10⁻⁶/° C., and most preferably not more than 2×10⁻⁶/° C. Herein, thelinear thermal expansion coefficient is a known physical value specificto materials.

Combinations of conductive base materials and dielectric having adifference in linear thermal expansion coefficient between them fallingwithin the range as described above will be listed below.

-   (1) A combination of pure titanium as conductive base material and a    thermal spray ceramic layer as a dielectric layer-   (2) A combination of pure titanium as conductive base material and a    glass lining layer as a dielectric layer-   (3) A combination of titanium alloy as conductive base material and    a thermal spray ceramic layer as a dielectric layer-   (4) A combination of stainless steel as conductive base material and    a glass lining layer as a dielectric layer-   (5) A combination of titanium alloy as conductive base material and    a thermal spray ceramic layer as a dielectric layer-   (6) A combination of stainless steel as conductive base material and    a glass lining layer as a dielectric layer-   (7) A combination of a composite of ceramic and iron as conductive    base material and a thermal spray ceramic layer as a dielectric    layer-   (8) A combination of a composite of ceramic and iron as conductive    base material and a glass lining layer as a dielectric layer-   (9) A combination of a composite of ceramic and aluminum as    conductive base material and a thermal spray ceramic layer as a    dielectric layer-   (10) A combination of a composite of ceramic and aluminum as    conductive base material and a glass lining layer as a dielectric    layer.

In view of the difference in the linear thermal expansion coefficient,the combinations of (1) through (4), and (7) through (10) above arepreferred.

Still another preferred embodiment of the dielectric coated electrodesof the invention capable of resisting high power is a dielectric coatedelectrode in which the dielectric layer has a thickness of from 0.5 to 2mm. The variation of the dielectric layer thickness is preferably notmore than 5%, more preferably not more than 3%, and still morepreferably not more than 1%.

As a method of thermally spraying ceramic as a dielectric onto the aboveconductive base material with high density and high adhesion, there isan atmospheric plasma spraying method. The atmospheric pressure plasmaspraying method refers to a technique in which fine particles or wiresof ceramic etc. are introduced into a source of plasma heat to form amelted or semi-melted particles, and the resulting particles are sprayedto a base material on which a layer is to be formed. The source ofplasma heat herein referred to is a high temperature plasma gas obtainedby heating gas molecules to high temperature to dissociate into atomsand applying further energy thereto to release electrons. The sprayingspeed of this plasma gas is high, and therefore the sprayed gas colloidsthe base material with a spray speed higher than that of a conventionalarc spraying or a flame spraying, providing a layer with high adhesionand higher density. A spraying method disclosed in Japanese PatentO.P.I. Publication Nos. 2000-301655 can be referred to in which a heatshielding layer is formed on material heated to high temperature.According to this method, it is possible to form a dielectric layer(thermally sprayed ceramic layer) having a void volume of not more than10% by volume, and further not more than 8% by volume.

In order to further reduce the void volume of the dielectric layer, itis preferred that a thermally sprayed layer such as the thermallysprayed ceramic layer is subjected to sealing treatment employing aninorganic compound. The inorganic compound is preferably a metal oxide,and more preferably one containing a silicon oxide (SiOx) as a maincomponent.

The inorganic compound for sealing is preferably one being hardenedthrough sol-gel reaction. When an inorganic compound for sealing is acompound containing a metal oxide as a main component, a metal alkoxideis coated on the ceramic spray layer as a sealing solution, and hardenedthrough sol gel reaction. When the inorganic compound for sealing is acompound containing silica as a main component, an alkoxysilane ispreferably used as a sealing solution.

In order to accelerate the sol gel reaction, energy treatment ispreferably carried out. Examples of the energy treatment include heathardening (hardening at not more than 200° C.) or UV irradiation. Asealing method, in which the alternate coating and hardening of dilutedsealing solution are repeated several times, provides an electrode withimproved inorganic property, with high density and without anydeterioration.

When in the preparation of the dielectric coated electrode of theinvention, a metal oxide solution as a sealing solution is coated on athermally sprayed ceramic layer and subjected to sealing treatment inwhich hardening is carried out through sol gel reaction, the metal oxidecontent after hardening is preferably not less than 60 mol %. When analkoxysilane is used as a metal alkoxide of a sealing solution, thecontent of SiOx (x: not more than 2) after hardening is preferably notless than 60 mol %. The content of SiOx (x: not more than 2) afterhardening is measured analyzing the section of the dielectric layerthrough an XPS.

The dielectric layer surface of the dielectric coated electrode issurface finished by polishing treatment so as to obtain a surfaceroughness Rmax (according to JIS B 0601) of not more than 10 μm, whichmakes it possible to maintain the dielectric layer thickness or a gapbetween the electrodes constant, provide stable discharge, and providean electrode with greatly increased durability, with high precision andwithout strain or cracking due to thermal shrinkage difference orresidual stress. It is preferred that at least the surface of thedielectric layer on the side contacting the substrate is surfacefinished by polishing.

A plasma discharge apparatus employing such an electrode will beexplained below employing FIGS. 1 through 6.

A plasma discharge apparatus is one which induces discharge in a gapbetween a roll electrode which is a grounding electrode and plural fixedelectrodes which are voltage application electrodes and face the rollelectrode, introduces a reactive gas to the gap to excite the reactivegas in a plasma state, and exposes a long length substrate provided onthe roll electrode to the reactive gas excited in a plasma state to forma layer on the substrate. Herein, the length in the transverse direction(perpendicular to the substrate transport direction) of the electrode isequal to that of the long length substrate. When a layer is formed onthe long length substrate within a region in the transverse directionshorter than the substrate width, considering that after the layerformation, the edges in the transverse direction of the substrate arecut off, the length in the transverse direction of the electrodedischarge surface may be equal to or greater than that of the region atwhich the layer is to be formed.

A plasma discharge apparatus carrying out the layer forming method ofthe invention is not limited to those described above, but may be anyone as long as a stable glow discharge is maintained and a reactive gasused for forming the layer is excited into a plasma state. As describedabove, a method comprising providing a substrate between electrodes andintroducing a reactive gas to a gap between the electrodes is preferablein that a large discharge area can be secured, and a layer with auniform thickness and with high performance can be formed. As anothermethod, there is a jetting method in which a substrate is provided ortransported to the vicinity of electrodes but not between theelectrodes, and then generated plasma is jetted to the substrate to forma layer on the substrate.

FIG. 1 shows a schematic drawing of one embodiment of the plasmadischarge vessel equipped in a plasma discharge apparatus used in thelayer forming method of the invention. In FIG. 1, substrate F with longlength is transported while wound around roll electrode 25 rotating inthe transport direction (clockwise in FIG. 1). Electrodes 26, which arefixed, are composed of plural cylinders and arranged to be opposed tothe roll electrode 25. The substrate F, which has been wound around theroll electrode 25, is pressed by nip rollers 65 and 66, transported intoa discharge space in the plasma discharge vessel 31 through guide roller64, subjected to discharge plasma treatment, and then transported intothe next process through guide roller 67. Blade 54 is provided at thevicinity of the nip rollers 65 and 66, and prevents air accompanied bythe transported substrate F from entering the plasma discharge vessel31. The volume of the accompanied air is preferably not more than 1% byvolume and more preferably 0.1% by volume, based on the total volume ofair in the plasma discharge vessel 31, which can be attained by the niprollers 65 and 66 above.

A mixed gas used in the discharge plasma treatment (an organic gascontaining both inert gas and reactive gas such as an organicfluorine-containing compound, a titanium compound, or a siliconcompound) is introduced into the plasma discharge vessel 31 from supplyport 52, and exhausted from exhaust port 53 after discharge treatment.

As in FIG. 1, FIG. 2 shows a schematic drawing of another embodiment ofthe plasma discharge vessel equipped in a plasma discharge apparatusused in the layer forming method of the invention. However, electrodes26 in FIG. 1, which are fixed and arranged to be opposed to the rollelectrode 25, are cylindrical, while electrodes 36 in FIG. 2 areprismatic.

As compared with cylindrical electrodes 26 shown in FIG. 1, prismaticelectrodes 36, as shown in FIG. 2, broaden the discharge region(discharge surface area), and are preferably used in the layer formingmethod of the invention.

FIG. 3 shows a schematic drawing of one embodiment of the cylindricalroll electrode described above, FIG. 4 shows a schematic drawing of oneembodiment of a cylindrical, fixed electrode, and FIG. 5 shows aschematic drawing of one embodiment of a prismatic, fixed electrode.

In FIG. 3, roll electrode 25 c, which is an electrode to be grounded, isan electrode in which a conductive base roll 25 a such as a metal rollis coated with a ceramic dielectric 25 b as a dielectric layer, thecoating being carried out by thermally spraying ceramic on the base rollto form a ceramic layer, and sealing the ceramic layer with sealingmaterials such as inorganic compounds. The ceramic dielectric layer hasa thickness of 1 mm, and is grounded. The ceramic material used forthermal spraying is preferably alumina, silicon nitride, and morepreferably alumina in view of easy processability. The dielectric layermay be provided on a conductive base roll by lining of inorganicmaterials. Materials for lining include silicate glass, borate glass,phosphate glass, germanate glass, tellurite glass, aluminate glass, andvanadate glass. Among these, borate glass is preferably used in view ofeasy processability. Examples of a metal used in the conductive baseroll 25 a include metals such as titanium, silver, platinum, stainlesssteel, aluminum, or iron, a composite of iron and ceramic, and acomposite of aluminum and ceramic. Stainless steel is preferable in viewof processability.

In one embodiment carried out in the invention, a base roll for the rollelectrode employs a stainless steel jacket roll having a cooling means(not illustrated in FIGS. ) employing chilled water. FIGS. 4 and 5 showfixed electrode 26 c and fixed electrode 36 c, respectively, which arevoltage application electrodes, and the electrodes have the sameconstitution as that of the roll electrode 25 c as described above. Thatis, the same dielectric layer as above is coated on a hollow stainlesssteel pipe, and the resulting electrode is constructed so as to becooled with chilled water during discharge. Fourteen fixed electrodesare arranged along the circumference of the roll electrode describedabove.

Power sources for applying voltage to the voltage application electrodeare not specifically limited. As the power sources, a high frequencypower source (200 kHz) produced by Pearl Kogyo Co., Ltd., a highfrequency power source (800 kHz) produced by Pearl Kogyo Co., Ltd., ahigh frequency power source (13.56 MHz) produced by Nippon Denshi Co.,Ltd., and a high frequency power source (150 MHz) produced by PearlKogyo Co., Ltd. can be used.

FIG. 6 shows a schematic view of one embodiment of the plasma dischargeapparatus used in the invention. In FIG. 6, plasma discharge vessel 36has the same construction as that of FIG. 2, and in addition, a gasgenerating device 51, a power source 41, and an electrode cooling device60 and so on are further provided. As a cooling agent used in theelectrode cooling device 60, insulating materials such as distilledwater and oil are used. Electrodes 25 and 36 shown in FIG. 6 are thesame as those illustrated in FIGS. 3, 4, and 5. The gap distance betweenthe opposed electrodes is, for example, approximately 1 mm.

The gap distance described above is determined considering thickness ofa dielectric layer provided on the electrode base roll, applied voltagelevel, or an object of employing plasma. When one of the opposedelectrodes described above has a dielectric layer or both opposedelectrodes described above have a dielectric layer, the minimum gapdistance between the electrode and the dielectric layer or between theboth dielectric layers is preferably 0.5 to 20 mm, and more preferably1±0.5 mm, in carrying out uniform discharge.

A mixed gas generated in the gas generating device 51 is introduced fromsupply port 52 in a controlled amount into a plasma discharge vessel 31,in which roll electrode 25 and fixed electrode 36 are arranged at apredetermined position, whereby the plasma discharge vessel is chargedwith the mixed gas, and thereafter, the gas is exhausted from theexhaust port 53. Subsequently, the roll electrode 25 being grounded,voltage is applied to electrodes 36 by power source 41 to generatedischarge plasma. From stock roll 61 in which substrate F is wounded,substrate F is transported to a gap between the electrodes in the plasmadischarge vessel 31 through guide roller 64 (so that the one side of thesubstrate contacts the surface of the roll electrode 25), subjected todischarge plasma treatment while transporting in the device to form alayer on the surface (CVD), and then transported to the next processingthrough guide roller 67. In the above, only the surface of the substrateopposite the surface contacting the roll electrode is subjected todischarge treatment.

The level of voltage applied to the fixed roll 36 by power source 41 isoptionally determined. For example, the voltage is 10 V to 10 kV, andfrequency of power source is adjusted to the range of from more than 100kHz to 150 MHz. Herein, as a power supply method, either a continuousoscillation mode (called a continuous mode) with a continuous sine waveor a discontinuous oscillation mode (called a pulse mode) carryingON/OFF discontinuously may be used, but the continuous mode is preferredin obtaining a uniform layer with high quality.

The vessel used in the plasma discharge vessel 31 is preferably a vesselof pyrex (R) glass, but a vessel of metal may be used if insulation fromthe electrodes is secured. For example, the vessel may be a vessel ofaluminum or stainless steel laminated with a polyimide resin or a vesselof the metal which is thermally sprayed with ceramic to form aninsulation layer on the surface.

When the substrate is made of resin, in order to minimize an influenceon the substrate during the discharge plasma treatment, the substratetemperature during the plasma discharge treatment is adjusted to atemperature of preferably from ordinary temperature (15 to 250° C.) toless than 200° C., and more preferably from ordinary temperature to notmore than 100° C. In order to adjust to the temperature within the rangedescribed above, the substrate or the electrodes are optionally cooledwith a cooling means during the discharge plasma treatment.

In the invention, the discharge plasma treatment is carried out atatmospheric pressure or at approximately atmospheric pressure. Herein,approximately atmospheric pressure herein referred to implies a pressureof 20 kPa to 110 kPa. In order to obtain the effects as described in theinvention, the pressure is preferably 93 kPa to 104 kpa.

In the electrodes for electric discharge used in the layer formingmethod of the invention, the maximum surface roughness Rmax of thesurface of the electrode on the side contacting the substrate isadjusted to preferably not more than 10 μm in obtaining the effects asdescribed in the invention, and adjusted to more preferably not morethan 8 μm, and still more preferably not more than 7 μm. Herein, themaximum surface roughness is one defined in JIS B 0161. In order toobtain the above range of Rmax, the electrode surface is preferablysubjected to polishing treatment. Further, the center-line averagesurface roughness (Ra) as defined in JIS B 0161 is preferably not morethan 0.5 μm, and more preferably not more than 0.1 μm.

A mixed gas used in the layer forming method of the invention will beexplained below.

A gas used when the layer forming method of the invention is carried outis basically a mixed gas of inert gas and a reactive gas for forming alayer, although it varies due to kinds of a layer formed on thesubstrate. The reactive gas content of the mixed gas is preferably 0.01to 10% by volume. As the layer to be formed, a layer having a thicknessof 1 nm to 1000 nm is formed.

The inert gas herein referred to implies an element belonging to groupXVIII in the periodic table, and is typically helium, neon, argon,krypton, xenon, or radon. In order to obtain the effects of theinvention, helium or argon is preferably used. In order to obtain alayer with high density and high precision, argon is most preferablyused as inert gas. It is assumed that use of argon is likely to generateplasma with high density. The argon content of the mixed gas ispreferably not less than 90% by volume, and more preferably not lessthan 95% by volume, based on the 100% by volume of mixed gas (a mixedgas of inert gas and reactive gas).

The reactive gas, which is a gas excited to plasma state at dischargespace, contains a component for forming a layer, for example, anorganometallic compound, an organic compound or an inorganic compound.

Employing, as the reactive gas, a gas containing for example, at leastone organometallic compound selected from zinc acetyl acetonate,triethylindium, trimethylindium, diethylzinc, dimethylzinc,tetraethyltin, and tetraoctyltin, a metal oxide layer can be formedwhich is useful for a medium refractive index layer such as a conductivelayer, an anti-static layer, or an anti-reflection layer. Employing, asthe reactive gas, a fluorine-containing compound, a water repellentlayer with a water repellent surface can be formed on a substrate, thesurface of which contains a fluorine-containing group lowering thesurface energy. Examples of the fluorine-containing compound include acarbon fluoride compound such as hexafluoropropylene (CF₃CFCF₂), oroctaf luorocyclobutane (C₄F₈) In view of safety, hexafluoropropylene oroctafluorocyclobutane, which does not generate a harmful gas such ashydrogen fluoride, can be used.

The substrate is treated in an atmosphere of a monomer containing ahydrophilic group and a polymerizable unsaturated bond in the molecule,and a hydrophilic polymerization layer can be deposited on the substratesurface. Examples of the hydrophilic group include a hydroxyl group, asulfonic acid group, a primary, secondary or tertiary amino group, anamido group, a quaternary ammonium group, a carboxylic acid group, and acarboxylic acid salt group. Use of a monomer containing a polyethyleneglycol chain can also form a hydrophilic polymerization. layer.

Examples of the monomer described above include acrylic acid,methacrylic acid, acryl amide, methacryl amide N,N-dimethylacryl amide,sodium acrylate, sodium methacrylate, potassium acrylate, potassiummethacrylate, styrene sulfonic acid sodium salt, allyl alcohol, allylamine, polyethylene glycol dimethacrylate, and polyethylene glycoldiacrylate, and at least one of these monomers can be used.

Further, use of a reactive gas containing an organic fluorine compound,a silicon compound or a titanium compound can form a low refractiveindex anti-reflection layer or a high refractive index layer. As theorganic fluorine compound, a fluorocarbon gas or a fluorohydrocarbon gasis preferably used. Examples of the fluorocarbon gas includetetrafluorocarbon, hexafluorocarbon, for example, tetrafluoromethane,tetrafluoroethylene, hexafluoropropylene, and octafluorocyclobutane.Examples of the fluorohydrocarbon gas include difluoromethane,tetrafluoroethane, tetrafluoropropylene, and trifluoropropylene.Further, fluorohydrocarbon halide compounds such asmonochlorotrifluoromethane, monochlorodifluoromethane ordichlorotetrafluorocyclobutane, or fluorinated organic compounds such asfluorinated alcohols, acids or ketones may be used, but the organicfluorine compound is not limited thereto. These compounds may have anethylenically unsaturated group in the molecule. These compounds may beused singly or as a mixture of two or more kinds thereof.

When the above organic fluorine compound is used in the mixed gas, thecontent of the organic fluorine compound in the mixed gas is preferably0.1 to 10% by volume, and more preferably 0.1 to 5% by volume, in that auniform layer is formed on a substrate by discharge plasma treatment.

When the organic fluorine compound in the invention is gas at ordinarytemperature and ordinary pressure, it can be used as it is in the mixedgas, wherein the method of the invention can be carried out most easily.When the organic fluorine compound in the invention is liquid or solidat ordinary temperature and ordinary pressure, it may be used as gas inwhich the compound is gasified by heating or under reduced pressure, oras a solution in which the compound is dissolved in an appropriatesolvent.

When the above titanium compound is used in the mixed gas, the contentof the titanium compound in the mixed gas is preferably 0.01 to 10% byvolume, and more preferably 0.01 to 5% by volume, in that a uniformlayer is formed on a substrate by the discharge plasma treatment.

As the reactive gas, a metal hydride compound, a metal halide compound,a metal hydroxide compound, or a metal peroxide compound can be used,and these may be optionally used in their gaseous state.

The mixed gas further containing hydrogen in an amount of 0.1 to 10% byvolume can markedly increase hardness of a layer formed on a substrate.

The mixed gas further containing a component selected from oxygen,ozone, hydrogen peroxide, carbon dioxide,. carbon monoxide, hydrogen andnitrogen in an amount of 0.01 to 5% by volume can accelerate reaction,and can form a layer with high density and high quality.

As the silicon compound or titanium compound described above, a metalhydride compound or a metal alkoxide compound is preferably used in viewof handling, and the alkoxide compound is more preferably used, since itis not corrosive, and generates no harmful gas nor causes contamination.

When the silicon compound or titanium compound is introduced into adischarge space or a gap between the electrodes, both compounds may bein the form of gas, liquid, or solid at ordinary temperature andordinary pressure. When they are gas at ordinary temperature andordinary pressure, they can be introduced in the discharge space as theyare. When they are liquid or solid, they are gasified by heating, orunder reduced pressure or ultrasonic wave radiation, and used. When thesilicon compound or the titanium compound is gasified and used, a metalalkoxide, which is liquid at ordinary temperature and has a boilingpoint of not more than 200° C., such as tetraethoxysilane or titaniumtetraisopropoxide, is suitably used in order to form an anti-reflectionlayer. The above metal alkoxide may be diluted with another solvent. Thesolvents include an organic solvent such as methanol, ethanol, n-hexaneor a mixture thereof. Since these solvents are decomposed duringdischarge plasma treatment, their influence on layer formation on thesubstrate or on composition of the formed layer during discharge plasmatreatment can be neglected.

As the above described silicon compound, for example, an organometalliccompound such as dimethylsilane or tetramethylsilane, a metallic hydridesuch as monosialne or disilane, a metal halide such as dichlorosilane ortrichlorosilane, an alkoxysilane such as tetramethoxysilane,tetramethoxysilane or dimethyldiethoxysilane, or an organosilane ispreferably used. The silicon compound used in the invention is notlimited thereto. These compounds may be used singly or as a mixture oftwo or more kinds thereof.

When the above silicon compound is used in the mixed gas, the content ofthe silicon compound in the mixed gas is preferably 0.1 to 10% byvolume, and more preferably 0.1 to 5% by volume, in that a uniform layeris formed on a substrate by the discharge plasma treatment.

As the above described titanium compound, for example, an organometalliccompound such as tetradimethylamino titanium, a metal hydride compoundsuch as titanium tetrahydride or dititanium hexahydride, a metal halidecompound such as titanium dichloride, titanium trichloride or titaniumtetrachloride, or a metal alkoxide compound such as titaniumtetraethoxide, titanium tetrapropoxide or titanium tetrabutoxide ispreferably used. The titanium compound used in the invention is notlimited thereto.

When an organometallic compound is added to a reactive gas, theorganometallic compound contains a metal selected from Li, Be, B, Na,Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Rb,Sr, Y, Zr, Nb, Mo, Cd, In, Ir, Sn, Sb, Cs, Ba, La, Hf, Ta, W, Tl, Pb,Bi, Ce, Pr, Nd, Pm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and theorganometallic compound is preferably one selected from a metalalkoxide, an alkylated metal, and a metal complex.

Various layers with high performance can be obtained properly selectingthe above reactive gas or a reactive gas other than the above reactivegas and employing the layer forming method of the invention. One examplethereof will be shown below, but the invention is not limited thereto.

-   Electrode membrane: Au, Al, Ag, Ti, Ti, Pt, Mo, Mo—Si-   Dielectric protective membrane: SiO₂, SiO, Si₃N₄, Al₂O₃, Al₂O₃, Y₂O₃-   Transparent conductive membrane: In₂O₃, SiO₂-   Electrochromic membrane: WO₃, IrO₂, MoO₃, V₂O₅-   Fluorescent membrane: ZnS, ZnS+ZnSe, ZnS+CdS-   Magnetic recording membrane: Fe—Ni, Fe—Si-Al, γ-Fe₂O₃, Co, Fe₃O₄,    Cr, SiO2, AlO₃-   Superconductive membrane: Nb, Nb—Ge, NbN-   Solar battery membrane: a-Si, Si-   Reflection membrane: Ag, Al, Au, Cu-   Selective absorption membrane: ZrC—Zr-   Selective transparent membrane: In₂O₃, SnO₂-   Anti-reflection membrane: SiO₂, TiO₂, SnO₂-   Shadow mask: Cr-   Anti-abrasion membrane: Cr, Ta, Pt, TiC, TiN-   Anti-corrosion membrane: Al, Zn, Cd, Ta, Ti, Cr-   Heat resistant membrane: W, Ta, Ti-   Lubricant membrane: MoS₂-   Decoration membrane: Cr, Al, Ag, Au, TiC, Cu

Next, the substrate used in the invention will be explained.

The substrate used in the invention may be in the form of film or in theform of stereoscopic body, for example, in the form of lens, as long asit can form a layer on its surface. When the substrate is one capable ofbeing provided between electrodes, a layer can be formed by placing thesubstrate in plasma generated between the electrodes, and when thesubstrate is one incapable of being provided between the electrodes, alayer can be formed by spraying the generated plasma to the substrate.

Materials constituting the substrate are not specifically limited, butresins are preferred in that discharge is a low temperature glowdischarge, and is carried out at atmospheric pressure or atapproximately atmospheric pressure.

For example, when the layer regarding the invention is ananti-reflection layer, the substrate is preferably a film of celluloseester such as cellulose triacetate, polyester, polycarbonate orpolystyrene, or one in which a gelatin layer, a polyvinyl alcohol (PVA)layer, an acryl resin layer, a polyester resin layer or a celluloseresin layer is coated on the above described film. As the substrate, asubstrate obtained by coating an anti-glare layer, a clear hard coatlayer, a backing layer or an anti-static layer on a support can be used.

Examples of the support (also used as the substrate) include a polyesterfilm such as a polyethylene terephthalate or polyethylene naphthalatefilm, a polyethylene film, a polypropylene film, a cellophane film, afilm of a cellulose ester such as cellulose diacetate, cellulose acetatebutyrate, cellulose acetate propionate, cellulose acetate phthalate,cellulose triacetate, cellulose nitrate or their derivative, apolyvinylidene chloride film, a polyvinyl alcohol film, anethylene-vinyl alcohol film, a syndiotactic polystyrene film, apolycarbonate film, a norbornene resin film, a polymethylpentene film, apolyetherketone film, a polyimide film, a polyethersulfone film, apolysulfone film, a polyetherketoneimide film, a polyamide film, afluorine-containing resin film, a nylon film, a polymethyl methacrylatefilm, an acryl film, and a polyarylate film.

These materials can be used singly or as a mixture of two or more kindsthereof. Commercially available materials such as Zeonecks (produced byNippon Zeon Co., Ltd.) or ARTON (produced by Nippon Gosei Gornu Co.,Ltd.) can be preferably used. Materials such as polycarbonate,polyacrylate, polysulfone and polyethersulfone, which have a highspecific birefringence, can be also used by properly adjusting asolution casting condition, a melt extrusion condition, or a stretchingcondition in the transverse or mechanical direction. The substrate inthe invention is not specifically limited to those described above. Asthe substrate in the invention, a film having a thickness of 10 to 1000μm is preferably used.

When in the product or optical film of the invention the layer formed onthe substrate is a layer for optical use such as an anti-reflectionlayer, a cellulose ester film is preferably used as the substrate in theinvention, since it provides a low reflection laminate. As the celluloseester, cellulose acetate, cellulose acetate butyrate, or celluloseacetate propionate is preferably used and cellulose acetate butyrate, orcellulose acetate propionate is more preferably used in effectivelyobtaining the effects of the invention.

When the above cellulose ester film is used as the substrate in theproduct or optical film of the invention, the cellulose ester filmpreferably contains a plasticizer.

The plasticizer used in the invention is not limited, but as theplasticizer, a phosphate plasticizer, a phthalate plasticizer, atrimellitate plasticizer, a pyromellitate plasticizer, a glycolateplasticizer, a citrate plasticizer, or a polyester plasticizer ispreferably used. Examples of the phosphate plasticizer include triphenylphosphate, tricresyl phosphate, cresyldiphenyl phosphate, octyldiphenylphosphate, diphenylbiphenyl phosphate, trioctyl phosphate, and tributylphosphate. Examples of the phthalate include diethyl phthalate,dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutylphthalate, di-2-ethylhexyl phthalate, and butylbenzil phthalate.Examples of the trimellitate plasticizer include tributyl trimellitate,triphenyl trimellitate, and trimethyl trimellitate. Examples of thepyromellitate plasticizer include tetrabutyl pyromellitate, tetraphenylpyromellitate, and tetraethyl pyromellitate. Examples of the glycolateplasticizer include triacetin, tributyrin, ethylphthalylethyl glycolate,methylphthalylethyl glycolate, and butylphthalylbutyl glycolate.Examples of the citrate plasticizer include triethyl citrate,tri-n-butyl citrate, acetyltriethyl citrate, acetyltri-n-butyl citrate,and acetyltri-n-(2-hexylethyl) citrate.

Examples of other carboxylic acid ester include butyl oleate,metylacetyl ricinolate, dibutyl sebacate, and various kinds oftrimellitic acid esters.

Examples of the polyester plasticizer include copolymers of dibasicacids such as aliphatic dibasic acids, alicyclic dibasic acids, oraromatic dibasic acids with glycols. The aliphatic dibasic acids are notspecifically limited, but examples of the aliphatic dibasic acidsinclude adipic acid, sebacic acid, phthalic acid, terephthalic acid, and1,4-cyclohexyldicarboxilic acid. Examples of the glycols includeethylene glycol, diethylene glycol, 1,3-propylene glycol, 1,2-propyleneglycol, 1,4-butylene glycol, 1,3-butylene glycol, and 1,2-butyleneglycol. These dibasic acids or glycols may be singly or as a mixture oftwo or more kinds thereof.

The plasticizer content of the cellulose ester film is preferably 1 to20% by weight based on the weight of the cellulose ester, in view offilm properties or processability.

When the layer formed on the substrate in the invention is ananti-reflection layer, it is preferred that the substrate (or supportitself) contains a UV absorbent in minimizing deterioration of a liquidcrystal.

The UV absorbent in the invention is preferably a UV absorbent which isexcellent in absorption of ultraviolet light having a wavelength of 370nm or less, and is less in absorption of visible light having awavelength of 400 nm or more in clearly displaying a liquid crystalimage. Examples of the UV absorbents preferably used in the inventioninclude an oxybenzophenone compound, a benzotriazole compound, asalicylic acid ester compound, a benzophenone compound, a cyanoacrylatecompound and a nickel complex compound, but are not limited thereto. Thepolymer UV absorbents described in Japanese Patent O.P.I. PublicationNo. 11-148430 are also preferably used.

The substrate in the invention preferably contains the UV absorbents asdisclosed in Japanese Patent Application No. 11-295209, having adistribution coefficient of not less than 9.2, since it provides reducedcontamination during discharge plasma treatment, and provides excellentcoatability of various layers. The UV absorbent having a distributioncoefficient of not less than 10.1 is especially preferably used.

When a cellulose ester film used as the substrate contains a UVabsorbent or a plasticizer, these compounds may bleed out from thesubstrate during discharge plasma treatment, and result in problem suchas contamination of a plasma discharge chamber due to their adherence tothe chamber or their adherence to the substrate. In order to solve theabove problem, a support comprising cellulose ester and a plasticizer ispreferably used which has a weight change before and after storage at80° C. and 90% RH falling within the range of ±2% by weight (retentionproperty). As such a cellulose ester film, a cellulose ester film asdisclosed in Japanese Patent Application No. 2000-338883 is preferablyused. For the purpose of the above, a polymer UV absorbent (or a UVabsorptive polymer) disclosed in Japanese Patent O.P.I. Publication No.6-148430 or in Japanese Patent Application No. 2000-156039 can bepreferably used. As a polymer UV absorbent, PUVA-30M (produced by OtsukaKagaku Co., Ltd.) is commercially available. A polymer UV absorbentrepresented by formula (1) or (2) disclosed in Japanese Patent O.P.I.Publication No. 6-148430 or a polymer UV absorbent represented byformula (3), (6) or (7) in Japanese Patent Application No. 2000-156039is especially preferably used.

When the layer formed on the substrate in the invention is ananti-reflection layer, a substrate having a retardation Ro in planes of0 to 1000 nm as the optical property is preferably used, and a substratehaving a retardation R_(t) in the thickness direction of 0 to 300 nm asthe optical property is preferably used according to its usage. Thewavelength dispersion property R₀(600)/R₀(450) of the substrate ispreferably from 0.7 to 1.3, and more preferably from 1.0 to 1.3.

Herein, R₀(450) represents a retardation in planes based on themeasurement of the three dimensional refractive index measured employinga 450 nm wavelength, and R₀(600) represents a retardation in planesbased on the measurement of the three dimensional refractive indexmeasured employing a 600 nm wavelength.

When the layer formed on the substrate in the invention is ananti-reflection layer, the layer is preferably a layer formed byproviding a polymerization layer on the substrate, polymerizing acomposition comprising one or more kinds of ethylenically unsaturatedmonomers, and by subjecting the resulting polymerization layer to plasmadischarge, in that adhesion between the layer formed by the plasmadischarge treatment and the substrate is enhanced. Particularly when thelayer, which has been formed by polymerizing a. composition comprisingone or more kinds of ethylenically unsaturated monomers, is treated witha solution having a pH of not less than 10, and then subjected todischarge plasma treatment, the adhesion is further enhanced. Herein,the solution having a pH of not less than 10 is preferably an aqueous0.1 to 3 mol/liter sodium hydroxide or potassium hydroxide solution.

As a resin layer formed by polymerizing a composition containing anethylenically unsaturated compound, a resin layer further containing anactive ray hardenable resin or a heat-hardenable resin as theconstitution component is preferably used, and the active ray hardenableresin layer is more preferably used.

The active ray hardenable resin layer herein referred to implies a layercontaining, as a main component, a resin which is irradiated by activerays such as UV light or electronic beam to be hardened. Examples of theactive ray hardenable resin include an ultraviolet (hereinafter referredto also as UV) ray hardenable resin or an electron beam hardenableresin. The active ray hardenable resin may be a resin which can behardened by active rays other than UV ray or electron beam.

The UV ray hardenable resins include a UV ray hardenable acrylurethaneresin, a UV ray hardenable polyesteracrylate resin, a UV ray hardenableepoxyacrylate resin, a UV ray hardenable polyolacrylate resin and a UVray hardenable epoxy resin.

The UV ray hardenable acrylurethane resin can be easily obtained byreacting a polyesterpolyol with an isocyanate monomer or its prepolymerand then reacting the resulting product with an acrylate having ahydroxy group such as 2-hydroxyethylacrylate, 2-hydroxyethylmethacrylate(hereinafter, the acrylate comprises methacrylate) or2-hydroxypropyl-acrylate (for example, Japanese Patent O.P.I.Publication No. 59-151110).

The UV ray hardenable polyesteracrylate resin can be easily obtained byreacting a polyesterpolyol with a monomer such as 2-hydroxyethylacrylateor 2-hydroxypropylacrylate (for example, Japanese Patent O.P.I.Publication No. 59-151112).

Examples of the UV ray hardenable epoxyacrylate resin include thoseobtained by reacting an epoxyacrylate oligomer in the presence of areactive diluting agent and a photoinitiator (Japanese Patent O.P.I.Publication No. 1-105738). Examples of the photoinitiator include abenzoine derivative, an oxime ketone derivative, a benzophenonederivative or a thioxanthone derivative. These initiators may be usedsingly or as a mixture of two or more kinds thereof.

Examples of the UV ray hardenable polyolacrylate resin includetrimethylolpropane triacrylate, ditrimethylolpropane tetracrylate,pentaerythritol tetracrylate, dipentaerythritol pentacrylate,dipentaerythritol hexacrylate or alkyl-modified dipentaerythritolpentacrylate.

These resins are usually used with a conventional photoinitiator. Theabove photoinitiator also works as a photo-sensitizer. Examples thereofinclude acetophenones, benzophenones, hydroxy benzophenones, Michler'sketone, α-amyloxime esters, and thioxanthones or their derivatives. Thephoto-sensitizers such as n-butylamine, triethylamine andtri-n-butylphosphine can be used together with the photoinitiator in thereaction of epoxyacrylates. The content of the photo-initiator orphoto-sensitizer used in the ultraviolet ray hardenable resin coatingcomposition, after the volatile solvent in the composition is removed bycoating and then drying, is preferably 2.5 to 6% by weight.

The polymerizable monomers having one unsaturated double bond in themolecule include methyl acrylate, ethyl acrylate, butyl acrylate, vinylacetate, benzyl acrylate, cyclohexyl acrylate, and styrene. Thepolymerizable monomers having two unsaturated double bonds in themolecule include ethylene glycol diacrylate, propylene glycoldiacrylate, divinylbenzene, 1,4-cyclohexane diacrylate,1,4-cyclohexyldimethyl diacrylate, trimethylol propane triacrylate, andpentaerythritol tetraacrylate.

The ultraviolet ray hardenable resins are selected from ADEKA OPTOMERKR-BY series: KR-400, KR-410, KR-550, KR-566, KR-567, or BY-320B (eachproduced by Asahi Denka Co., Ltd.); Koei Hard A-101-KK, A-101-WS, C-302,C-401-N, C-501, M-101, M-102, T-102, D-102, NS-101, FT-102Q8, MAG-1-P20,AG-106, or M-101-C, (each produced by Koei Kagaku Co., Ltd.); SEIKA BEAMPHC 2210 (S), PHC X-9 (K-3), PHC 2213, DP-10, DP-20, DP-30, P1000,P1100, P1200, P1300, P1400, P1500, P1600, or SCR 900 (each produced byDainichi Seika Kogyo Co., Ltd.); KRM7033, KRM7039, KRM7130, KRM7131,UVCRYL29201, or UVCRYL29202 (each produced by Daicel-UCB Co., Ltd.);RC-5015, RC-5016, RC-5020, RC-5031, RC-5100, RC-5102, RC-5120, RC-5122,RC-5152, RC-5171, RC-5180, or RC-5181 (each produced by Dainippon Inkand Chemicals, Inc.); AUREX No. 340 Clear (produced by Chugoku ToryoCo., Ltd.); SANRAD H-601 (produced by Sanyo Chemical Industries, Ltd.);SP-1509 or SP-1507 (each produced by Showa Kobunshi Co., Ltd.); RCC-15C(produced by Grace Japan Co., Ltd.); and ARONIX M-6100, M-8030, orM-8060 (produced by Toa Gosei Co., Ltd.); and other resins which areavailable on the market.

The active ray hardened layer used in the invention can be providedaccording to a conventional method. As a light source for hardening anactive ray hardenable layer due to photo-hardening reaction to form ahardened layer, any light source capable of emitting UV rays can beused. Examples of the light source include a low pressure mercury lamp,a medium pressure mercury lamp, a high pressure mercury lamp, asuper-high pressure mercury lamp, a carbon arc lamp, a metal halidelamp, and a xenon lamp.

Although the exposure amount is varied depending on the kinds of lightsource, it may be 20-10,000 mJ/cm², and is preferably 50-2,000 mJ/cm².The sensitizer having an absorption maximum in the range of fromnear-ultraviolet to visible wavelength is used.

The solvents for preparing the coating solution of the active rayhardenable resin layer can be suitably selected from the solvents usedin the above backing layer or conductive fine particle-containing layer,for example, hydrocarbons, alcohols, ketones, esters, glycols, othersolvents or a mixture thereof. It is preferred that the solvent is asolvent containing, in an amount of preferably not more than 5% byweight and more preferably 5 to 80% by weight, propylene glycolmonoalkyl (alkyl having 1 to 4 carbon atoms) ether or propylene glycolmonoalkyl (alkyl having 1 to 4 carbon atoms) ether ester.

The coating solution of the ultraviolet ray hardenable resin compositionis coated through a gravure coater, a spinner coater, a wire bar coater,a roll coater, a reverse-roll coater, an extrusion coater or anair-doctor coater, and the wet coating thickness is preferably 0.1 to 30μm, and more preferably 0.5 to 15 μm. The coating speed is preferably 10to 60 m/minute.

The coated layer after dried is irradiated with ultraviolet rays forpreferably 0.5 seconds to 5 minutes, and more preferably 3 seconds to 2minutes, in view of hardening efficiency of. the ultraviolet rayhardenable resin or workability.

The hardened layer preferably contains inorganic or organic fineparticles in order to prevent blocking or to increase abrasionresistance. The inorganic fine particles include silicon oxide, titaniumoxide, aluminum oxide, tin oxide, zinc oxide, calcium carbonate, bariumsulfate, talc, kaolin and calcium sulfate. The organic fine particlesinclude polymethacrylic acid-methylacrylate resin particles,acrylstyrene resin particles, polymethylmethacrylate resin particles,silicon resin particles, polystyrene resin particles, polycarbonateresin particles, benzoguanamine resin particles, melamine resinparticles, polyolefin resin particles, polyester resin particles,polyamide resin particles, polyimide resin particles and polyethylenefluoride resin particles. These particles can be added to theultraviolet ray hardenable resin composition. These particles have anaverage particle size of preferably 0.005 to 1 μm, and more preferably0.01 to 0.1 μm.

The content of the particles is preferably 0.1 to 10 parts by weightbased on the 100 parts by weight of the ultraviolet ray hardenable resincomposition.

The hardened layer formed by hardening a UV hardenable resin layer maybe a clear hard coat layer with a center-line surface roughness Ra of 1to 50 nm, or an anti-glare layer with an Ra of 0.1 to 1 μm. In theinvention, these layers can be subjected to plasma treatment. Accordingto the method of the invention, a uniform optical interference layersuch as a high refractive index layer or a low refractive index layercan be provided on the uneven surface of the substrate. It is preferredthat uniform plasma treatment is carried out on an anti-glare layer witha center-line average surface roughness Ra defined in JIS B 0601 of 0.1to 0.5 μm to form a layer.

When the layer in the invention is formed on the substrate as describedabove, the thickness deviation from the average thickness of the layerfalls within the range of preferably ±10%, more preferably ±5%, andstill more preferably ±1%.

When a product or optical film having an anti-reflection layer on asubstrate is prepared in the invention, the surface of the substratebefore subjected to plasma treatment is preferably irradiated with UVrays, whereby adhesion of the layer to the substrate surface isenhanced. The UV ray irradiation amount after plasma treatment ispreferably 50 to 2000 mJ/cm². The UV ray irradiation amount less than 50mJ/cm² may not provide good results, and the UV ray irradiation amountexceeding 2000 mJ/cm² may result in deformation of the substrate. Plasmatreatment is carried out in preferably one hour and more preferably inten minutes after the UV ray irradiation. The UV ray irradiation beforethe plasma treatment may be carried out at the same time as the UV rayirradiation for hardening the UV ray hardenable resin as describedabove. In this case, the UV ray irradiation is preferably carried out inan irradiation amount more than a minimum irradiation amount requiredfor the hardening.

When in the invention an anti-reflection layer is prepared, it iseffective that the layer is subjected to plasma treatment and then to UVray irradiation, since the layer is quickly stabilized.

For this purpose, the layer surface subjected to plasma treatment ispreferably irradiated with UV ray in an irradiation amount of 50 to 2000mJ/cm². This irradiation is preferably carried out after plasmatreatment and before the irradiated substrate is wound around a core.The substrate subjected to the plasma treatment is preferably treatedfor 1 to 30 minutes in a drying zone maintained at 50 to 130° C.

Both surfaces of a product or optical film having an anti-reflectionlayer on the substrate in the invention are preferably subjected toplasma treatment, since curl is reduced. Each surface of the substratemay be subjected to plasma treatment, separately, but it is preferredthat both surfaces of the substrate are simultaneously subjected toplasma treatment. The surface of the substrate opposite the lowreflection layer is preferably subjected to backing treatment due toplasma treatment. As the backing treatment, there is, for example, anadhesion enhancing treatment as disclosed in Japanese Patent ApplicationNo. 2000-273066, or an anti-static treatment as disclosed in JapanesePatent Application No. 2000-80043. The backing treatment is not limitedto these treatments.

In the invention, the product or optical film having on the substrate ametal oxide layer, which works as, for example, an anti-reflectionlayer, preferably comprises a high refractive index layer with arefractive index of 1.6 to 2.4 containing titanium oxide as a maincomponent. It is preferred that in addition to the above high refractiveindex layer, a low refractive index layer with a refractive index of 1.3to 1.5 containing silicon oxide as a main component is continuouslyprovided on the substrate, which provides good adhesion between thelayers. It is more preferred that immediately after an ultraviolethardened layer is provided on a substrate, the layer is subjected toplasma treatment to form a high refractive index layer and a lowrefractive index layer on the substrate.

The refractive index of the above high refractive index layer containingtitanium oxide as a main component is especially preferably not lassthan 2.2. Such a high refractive index metal oxide layer can be formedaccording to the layer forming method of the invention.

The metal oxide layer such as a layer containing titanium oxide as amain component has a carbon content of preferably from 0.1 to 5% byweight, in view of its flexibility or its adhesion to a lower layer. Thecarbon content of the metal oxide layer is more preferably 0.2 to 5% byweight, and still more preferably 0.3 to 3% by weight. This carboncontent range also applies to that of the low refractive index layercontaining silicon oxide as a main component as described above.

The above carbon content range in the above metal oxide layer such asthe anti-reflection layer similarly applies to another layer such as alayer of a metal, another metal oxide, a metal nitride or a metalboride. When a substrate is subjected to plasma treatment employing areactive gas containing an organic compound, a layer containing a carbonatom is formed on the substrate, and therefore, the plasma treatmenteasily provides a layer having a carbon content of the above range. Theabove carbon content range is preferable in not only the layer formed byplasma treatment but also in another layer, since the range providesimproved flexibility or adhesion. However, too low a carbon contenttends to produce cracks in the formed layer, and too high a carboncontent tends to change a refractive index with time and lower abrasionresistance, which is undesirable.

EXAMPLES

The invention will be detailed according to the following examples, butis not limited thereto.

(Preparation of Dielectric Coated Electrode Set A of the Invention)

In the plasma discharge apparatus of FIG. 2, a set of a dielectriccoated roll electrode and plural dielectric coated prismatic electrodeswas prepared as follows:

In a roll electrode 25 of FIG. 2, a stainless steel jacket roll basematerial having a cooling device (not illustrated in FIG. 2) employingchilled water was coated with an alumina thermal spray layer with highdensity and high adhesion according to an atmospheric plasma method toobtain a roll electrode with a roll diameter of 1000 mm. After that, asolution prepared by diluting tetramethoxysilane with ethyl acetate wascoated on the resulting electrode, dried and hardened by UV rayirradiation to carry out sealing treatment. Thus, a roll electrodehaving a dielectric layer was obtained. The dielectric layer surface ofthe roll electrode was polished, smoothed, and processed to give an Rmaxof 5 μm.

The thus obtained dielectric layer had a void volume of 5% by volume.The dielectric layer had an SiOx content of 75 mol %. The thickness ofthe dielectric layer was 1 mm (the layer thickness variation fallingwithin the range of ±1%). The relative dielectric constant of thedielectric was 10. The difference in linear thermal expansioncoefficient between the conductive base material and the dielectric was9.8×10⁻⁶/° C.

The resulting roll electrode 25 was grounded.

The same dielectric layer as above was coated on hollow, prismatic puretitanium pipes under the same condition as above. Thus, a group ofcounter electrodes opposed to the roll electrode was prepared as a groupof voltage application electrodes. The dielectric layer of the voltageapplication electrodes had the same physical properties as that of theabove roll electrode, but in the voltage application electrodes thedifference in linear thermal expansion coefficient between theconductive base material and the dielectric was 1.7×10⁻⁶/° C. The totaldischarge surface area of the voltage application electrodes was 15000cm²{=150 cm (length in the transverse direction)×2 cm (length in thetransport direction)×50 (the number of counter electrodes)}

The thus obtained electrode set having the opposed electrodes had a heatresistance of 200° C., a voltage endurance of not less than 10 kV, and amaximum output of not less than 400 kW/m². Even when continuousdischarge was carried out for 240 hours, no damage was observed in theelectrode set.

(Preparation of Dielectric Coated Electrode Set B of the Invention)

A dielectric coated electrode set B was prepared in the same manner asin dielectric coated electrode set A above, except that a stainlesssteel pipe was used instead of the hollow, prismatic pure titanium pipeused for preparation of the voltage application electrode. Thiselectrode set B had the same Rmax, SiO₂ content, dielectric layerthickness, and relative dielectric constant as those of electrode set A,but in the voltage application electrode the difference in linearthermal expansion coefficient between the conductive base material andthe dielectric was 9.8×10⁻⁶/° C.

The thus obtained electrode set B having the opposed electrodes had aheat resistance of 120° C., a voltage endurance of not less than 10 kV,and a maximum output of not less than 400 kW/m². Even when continuousdischarge was carried out for 240 hours, no damage was observed in theelectrode set.

(Preparation of Dielectric Coated Electrode Set C of the Invention)

In a roll electrode 25 of FIG. 2, a stainless steel jacket roll basematerial having a cooling device (not illustrated in FIG. 2) employingchilled water was coated with two dielectric layers each having adifferent void volume according to a glass lining method to obtain aroll electrode with a roll diameter of 200 mm. The lower dielectriclayer had a thickness of 0.3 mm and a void volume of 25% by volume. Theupper dielectric layer had a thickness of 0.7 mm and a void volume of 3%by volume. Further, the dielectric layer surface of the roll electrodewas polished, smoothed, and processed to give an Rmax of 5 μm.

The thus obtained dielectric layer had a void (having an opening on thelayer surface) volume of 0% by volume. The final thickness of thedielectric layer was 1 mm (the layer thickness variation falling withinthe range of ±1%). The relative dielectric constant of the dielectricwas 6.1. The difference in linear thermal expansion coefficient betweenthe conductive base material and the dielectric was 5.3×10⁻⁶/° C.

resulting roll electrode 25 was grounded.

The same dielectric layer as above was coated on a hollow, prismaticstainless steel pipe employing the same glass lining method as above.Thus, a group of counter electrodes opposed to th roll electrode wasprepared as a group of voltage application electrodes. The totaldischarge surface area of the voltage application electrodes as 15000cm²{=150 cm (length in the transverse direction)×2 cm (length in thetransport direction)×50 (the number of voltage application electrodes)}

The thus obtained electrode set having the opposed electrodes had a heatresistance of 100° C., a voltage endurance of not less than 10 kV, and amaximum output of not less than 200 kW/m². Even when continuousdischarge was carried out for 240 hours, no damage was observed in theelectrode set.

(Preparation of Comparative Dielectric Coated Electrode Set)

Comparative dielectric coated electrode set was prepared in the samemanner as in dielectric coated electrode set, except that the aluminathermal spray layer coating method was carried out employing a flamespray method instead of the atmospheric plasma method.

The thus obtained dielectric layer had a void volume of 11% by volume.The thus obtained electrode set having the opposed electrodes had a heatresistance of 80° C., a voltage endurance of 2 kV. The maximum output ofthis electrode set was 8 kW/m² (0.8 kW/cm²), and could not attainintended output.

(Preparation of Substrate)

A cellulose ester film as a substrate was prepared according to thefollowing procedure:

<<Preparation of Dope C>>

(Preparation of Silicon Oxide Dispersion Liquid A) Aerosil 2000V 1 kg(produced by Nihon Aerosil Co., Ltd.) Ethanol 9 kg

The above composition was mixed with stirring in a dissolver for 30minutes, and dispersed in a mantongorin type high pressure disperser toobtain Silicon oxide dispersion liquid A.

(Preparation of Solution B) Cellulose triacetate (acetyl substitution 6kg degree: 2.65) Methylene chloride 140 kg

The above composition was incorporated in a sealed vessel, heated withstirring, and filtered to obtain a solution. The resulting solution wasadded with stirring to 10 kg of the above-obtained Silicon oxidedispersion liquid A, stirred for additional three hours, and filtered toobtain Solution B.

(Preparation of Base Dope C) Methylene chloride 440 kg Ethanol 35 kgCellulose triacetate (acetyl substitution 100 kg degree: 2.65) Triphenylphosphate 8 kg Ethylphthalylethylglycolate 3 kg TINUVIN 326 (produced by0.4 kg Ciba Speciality Chemicals Co. Ltd.) TINUVIN 109 (produced by 0.9kg Ciba Speciality Chemicals Co. Ltd.) TINUVIN 171 (produced by 0.9 kgCiba Speciality Chemicals Co. Ltd.)

The above dope composition was incorporated in a sealed vessel, andstirred while heating to obtain a solution. The resulting solution wascooled to a temperature to be cast on a support, allowed to standovernight, defoamed, and filtered employing an Azumi Roshi No. 244produced by Azumi Roshi Co., Ltd. to obtain Base dope C. Subsequently,Solution B was added to the Base dope C at an addition rate of 2 kg per100 kg of the Base dope C, uniformly mixed in an in-line mixer (a staticin-line mixer Hi-Mixer SWJ, produced by Toray Co. Ltd.), and filtered toobtain Dope C.

<<Preparation of Dope E>>

(Preparation of Silicon Oxide Dispersion Liquid A) Aerosil R972V(average primary particle size: 16 nm, 1 kg produced by Nihon AerosilCo., Ltd.) Ethanol 9 kg

The above composition was mixed with stirring in a dissolver for 30minutes, and dispersed in a mantongorin type high pressure disperser toobtain Silicon oxide dispersion liquid A.

(Preparation of Solution D) Cellulose acetate propionate (acetyl 6 kgsubstitution degree: 2.0, propionyl substitution degree: 0.8) Methylacetate 100 kg Ethanol 40 kg

The above composition was incorporated in a sealed vessel, heated withstirring, and filtered to obtain a solution. The resulting solution wasadded with stirring to 10 kg of the above-obtained Silicon oxidedispersion liquid A, stirred for additional three hours, and filtered toobtain Solution D.

(Preparation of Base Dope E) Cellulose acetate propionate (acetyl 100 kgsubstitution degree: 2.0, propionyl substitution degree: 0.8) Methylacetate 290 kg Ethanol 85 kg KE-604 (produced by Arakawa 15 kg KagakuKogyo Co., Ltd.) PUVA-30M (produced by Otsuka 5 kg Kagaku Co., Ltd.)

The above dope composition was incorporated in a sealed vessel, andstirred while heating to obtain a solution. The resulting solution wascooled to a temperature to be cast on a support, allowed to standovernight, defoamed, and filtered employing an Azumi Roshi No. 244produced by Azumi Roshi Co., Ltd. to obtain a Base dope E. Subsequently,Solution D was added to the Base dope E at an addition rate of 2 kg per100 kg of the Base dope E, uniformly mixed in an in-line mixer (a staticin-line mixer Hi-Mixer SWJ, produced by Toray Co. Ltd.), and filtered toobtain a Dope E.

<<Preparation of Dope G>>

(Preparation of Silicon Oxide Dispersion Liquid F) Aerosil 200V(produced by Nihon Aerosil Co., Ltd.) 1 kg Ethanol 9 kg

The above composition was mixed with stirring in a dissolver for 30minutes, and dispersed in a mantongorin type high pressure disperser toobtain Silicon oxide dispersion liquid F.

(Preparation of Solution E) Cellulose triacetate (acetyl substitution 6kg degree: 2.88) Methylene chloride 140 kg

The above composition was incorporated in a sealed vessel, heated withstirring, and filtered to obtain a solution. The resulting solution wasadded with stirring to 10 kg of the above-obtained Silicon oxidedispersion liquid F, stirred for additional three hours, and filtered toobtain Solution E.

(Preparation of Base Dope G) Methylene chloride 440 kg Ethanol 35 kgCellulose triacetate (acetyl substitution 100 kg degree: 2.88) Triphenylphosphate 9 kg Ethylphthalylethylglycolate 4 kg TINUVIN 326 (produced by0.4 kg Ciba Speciality Chemicals Co. Ltd.) TINUVIN 109 (produced by 0.9kg Ciba Speciality Chemicals Co. Ltd.) TINUVIN 171 (produced by 0.9 kgCiba Speciality Chemicals Co. Ltd.)

The above dope composition was incorporated in a sealed vessel, andstirred while heating to obtain a solution. The resulting solution wascooled to a temperature to be cast on a support, allowed to standovernight, defoamed, and filtered employing an Azumi Roshi No. 244produced by Azumi Roshi Co., Ltd. to obtain a Base dope G. Subsequently,Solution E was added to the Base dope G at an addition rate of 2 kg per100 kg of the Base dope G, uniformly mixed in an in-line mixer (a staticin-line mixer Hi-Mixer SWJ, produced by Toray Co. Ltd.), and filtered toobtain a Dope G.

The acyl substitution degree of the cellulose ester used in the abovedopes C, E and G was measured according to a method described below.

<<Measurement of the Acyl Substitution Degree of the Cellulose Ester>>

The substitution degree was measured according to a method as describedin ASTM-D817-96.

<<Preparation of Cellulose Ester Film>>

Cellulose ester films 1 through 3 were prepared employing the abovedopes C, E and G, according to the following procedures.

(Preparation of Cellulose Ester Film 1)

Dope C was filtered, and was uniformly cast at a dope temperature of 35°C. on a 30° C. stainless steel belt support to form a web, employing abelt casting apparatus. The web was dried until it could be peeled fromthe support, and then was peeled from the support. At peeling, theresidual solvent amount of the web was 35%.

The peeled web was dried at 115° C. while holding both side edges of theweb film, released from the holding, further dried in a dry zone of 120°C. while transported by rollers, and subjected to knurling treatment togive a protrusion a 5 μm height and a 10 mm width at the both sideedges. Thus, cellulose ester film 1 with a thickness of 80 μm wasprepared. The film width was 1300 mm, and the film winding length was1500 m.

(Preparation of Cellulose Ester Films 2 and 3)

Cellulose ester film 2 with a thickness of 80 μm was prepared in thesame manner as in cellulose ester film 1, except that Dope E was usedinstead of Dope C. Cellulose ester film 3 with a thickness of 80 μm wasprepared in the same manner as in Cellulose ester film 2, except thatDope G was used instead of Dope E.

The cellulose ester films 1, 2, and 3 were measured for retentionproperty according to the method as described later. The retentionproperty of films 1, 2, and 3, which was determined from the weightvariation before and after the films were stored at 80° C. and at 90% RHfor 48 hours, was 5.1%, 0.4%, and 5.0%, respectively.

<<Evaluation of Retention Property>>

Each of the films was cut to a size of 10 cm×10 cm, allowed to stand at23° C. and at 55% RH for 24 hours, and weighed. Then, the film wassubjected to heat treatment in which the film was stored at 80° C. andat 90% RH for 48 hours, and then the surface of the film was softlywiped. Thereafter, the resulting film was again allowed to stand at 230C and at 55% RH for 24 hours, and then weighed. The retention propertyis represented by the following formula:Retention Property (%)={Film weight before heat treatment−Film weightafter heat treatment}×100/Film weight before heat treatment<<Preparation of Film Substrate>>

Film substrates were prepared employing cellulose ester films 1, 2, and3, as follows:

(Preparation of Film Substrate 1)

Cellulose ester film 1 itself was designated as film substrate 1.

(Preparation of Film Substrate 2)

The following coating composition (2) was extrusion coated on onesurface b of cellulose ester film 1 to give a wet thickness of 13 μm,dried in a drying zone of 80° C., and subjected to ultraviolet lightirradiation at 120 mJ/cm² to obtain a clear hard coat layer with a drythickness of 4 μm and a center line average surface roughness (R_(a)) of15 nm. The surface b herein referred to means the surface of the webcontacting the belt support in the dope casting film manufacture.

(Preparation of Film Substrate 3)

The following coating composition (3) was extrusion coated on onesurface b of cellulose ester film 1 to give a wet thickness of 13 μm,dried in a drying zone of 80° C., and subjected to ultraviolet lightirradiation at 120 mJ/cr² to obtain an antiglare layer with a drythickness of 5 μm and a center line average surface roughness (R_(a)) of0.3 μm. The surface b herein referred to means the surface of the webfilm facing the belt support at the dope casting.

(Preparation of film substrates 4 through 6)

Film substrates 4 through 6 were prepared in the same manner as in Filmsubstrates 1 through 3, respectively, except that cellulose ester film 2was used instead of cellulose ester film 1.

(Preparation of Film Substrates 7 through 9)

Film substrates 7 through 9 were prepared in the same manner as in Filmsubstrates 1 through 3, respectively, except that cellulose ester film 3was used instead of cellulose ester film 1. Herein was used a celluloseester film 3 having a back coating layer on the other surface a of thefilm (opposite the surface b). That is, before the clear hard coat layeror anti-glare layer was coated, the following coating composition (1)had been extrusion coated on the other surface a of cellulose ester film3 to give a wet thickness of 13 μm, dried at 80° C. to obtain a backcoating layer.

The coating compositions (1) and (2) used in the preparation of theabove film substrates and the preparation method of coating composition(3) are shown below. Coating composition (1) (Back coating layer coatingcomposition) Acetone 30 parts by weight Ethyl acetate 45 parts by weightIsopropyl alcohol 10 parts by weight Diacetyl cellulose 0.5 parts byweight 2% silica fine particle acetone dispersion 0.1 parts by weightliquid (Aerosil 200V, produced by Nihon Aerosil Co., Ltd.) Coatingcomposition (2) (Clear hard coat (CHC) layer coating composition)Dipentaerythritol hexacrylate monomer 60 parts by weightDipentaerythritol hexacrylate dimmer 20 parts by weightDipentaerythritol hexacrylate trimer 20 parts by weight or polymerhigher than the trimer Dimethoxybenzophenone 4 parts by weight(photo-initiator) Ethyl acetate 50 parts by weight Methyl ethyl ketone50 parts by weight Isopropyl alcohol 50 parts by weight Preparation ofCoating composition (3) (Anti-glare coating layer coating composition)Ethyl acetate 50 parts by weight Methyl ethyl ketone 50 parts by weightIsopropyl alcohol 50 parts by weight Silycia 431 (average particle size:2.5 μm, 2.5 parts by weight produced by Fuji Silysia Chemical Co., Ltd.)Aerosil R972V (average particle size: 16 nm, 2 parts by weight producedby Nihon Aerosil Co., Ltd.)

The above composition was stirred in a high speed stirrer TK Homomixer(produced by Tokushu Kika Kogyo Co., Ltd.), further dispersed in acollision type disperser Mantongorin (produced by Gorin Co., Ltd.), andthen added with the following components to obtain a coating composition(3). Dipentaerythritol hexacrylate monomer 60 parts by weightDipentaerythritol hexacrylate dimmer 20 parts by weightDipentaerythritol hexacrylate trimer 20 parts by weight or polymerhigher than the trimer Dimethoxybenzophenone 4 parts by weight(photo-initiator)

The above obtained film substrates 1 through 9 are shown in Table 1.TABLE 1 Film Coating layer Coating layer substrate Support on surface“a” on surface “b” Film Cellulose None None substrate 1 ester film 1Film Cellulose None Clear hard substrate 2 ester film 1 coat layer FilmCellulose None Anti-glare substrate 3 ester film 1 layer Film CelluloseNone None substrate 4 ester film 2 Film Cellulose None Clear hardsubstrate 5 ester film 2 coat layer Film Cellulose None Anti-glaresubstrate 6 ester film 2 layer Film Cellulose Back coating Nonesubstrate 7 ester film 3 layer Film Cellulose Back coating Clear hardsubstrate 8 ester film 3 layer coat layer Film Cellulose Back coatingAnti-glare substrate 9 ester film 3 layer layer

Example 1

<<Preparation of Optical Film>>

Optical films 8A through 80 having the anti-reflection layers as shownin Table 2 were prepared employing film substrate 8 as shown in Table 1and employing a plasma discharge apparatus as shown in FIG. 6 equippedwith the plasma discharge vessel as shown in FIG. 2 in which thedielectric coated electrode set B of the invention as prepared above isinstalled.

As the power sources for plasma generation, a high frequency powersource (50 kHz) produced by Shinko Denki Co. Ltd, an impulse highfrequency power source (100 kHz, used with continuous mode) produced byHeiden Kenkyuusho, a high frequency power source (200 kHz) produced byPearl Kogyo Co., Ltd., a high frequency power source (800 kHz) producedby Pearl Kogyo Co., Ltd., a high frequency power source (13.56 MHz)produced by Nippon Denshi Co., Ltd., and a high frequency power source(150 MHz) produced by Pearl Kogyo Co., Ltd. were used.

<<Discharge Condition>>

Discharge output was varied between 0.1 to 100 W/cm².

<<Reactive Gas>>

The composition of a mixed gas (reaction gas) used in the plasmatreatment will be shown below.

(Composition for Forming a Titanium Oxide Layer)

-   Inert gas: argon 98.75% by volume-   Reactive gas 1: a hydrogen gas (1% based on the total mixed gas)-   Reactive gas 2: tetraisopropoxytitanium vapor (liquid heated to    150° C. was bubbled with argon gas) 0.25% by volume based on the    total reaction gas.

The hard coat layer of film substrate 8 was continuously subjected toatmospheric pressure plasma treatment under the above dischargecondition employing the above reactive gas to obtain a 100 nm layer onthe hard coat layer. The refractive index of the resulting layer wasmeasured.

<<Measurement of Refractive Index and Layer Thickness>>

The spectral reflectance of the resulting layer was measured undercondition of a 5° regular reflection through a spectrophotometer TYPE1U-4000 (produced by Hitachi Seisakusho Co., Ltd.). In order to preventlight reflection from the rear surface of the optical film opposite theobserver side, the rear surface was surface-roughened, and subjected tolight absorbing treatment employing with black spray to form a lightabsorbing layer. Reflectance of the resulting film was measuredemploying a wavelength of from 400 nm through 700 nm. An opticalthickness was calculated from λ/4 of the spectra, and then refractiveindex was calculated based on the aforementioned. Further, the layerthickness was calculated from the results of the reflection spectra.Herein a refractive index measured employing a 550 nm light was adoptedas a representative value. TABLE 2 Power source frequency DischargeRefractive (sine wave) output index Remarks Optical 200 kHz 1.2 W/cm²2.2 Invention film 8A Optical 200 kHz 25 W/cm² 2.32 Invention film 8BOptical 800 kHz 1.2 W/cm² 2.25 Invention film 8C Optical 800 kHz 25W/cm² 2.34 Invention film 8D Optical 13.56 MHz 1.2 W/cm² 2.28 Inventionfilm 8E Optical 13.56 MHz 25 W/cm² 2.34 Invention film 8F Optical 150MHz 1.2 W/cm² 2.22 Invention film 8G Optical 150 MHz 25 W/cm² 2.31Invention film 8H Optical 50 kHz 1.2 W/cm² 1.75 Comparative film 8IOptical 50 kHz 25 W/cm² 1.8 Comparative film 8J Optical 100 kHz 0.8W/cm² 1.81 Comparative film 8K Optical 100 kHz 1.2 W/cm² 1.85Comparative film 8L Optical 200 kHz 0.8 W/cm² 1.88 Comparative film 8MOptical 13.56 MHz 0.8 W/cm² 1.9 Comparative film 8N Optical 150 MHz 0.8W/cm² 1.9 Comparative film 8O

As is apparent from Table 2, each of the inventive optical films 8Athrough 8H provides improved refractive index and a layer with highquality.

Example 2

<<Preparation of Optical Film>>

Optical films 22 through 32 were prepared employing film substrates 1through 9 and employing the same plasma discharge apparatus asExample 1. The preparation was carried out as follows.

In the preparation of optical films 22 through 30, a roll electrodehaving a dielectric layer with an Rmax of 5 μm was employed, and a 20W/cm² power (total power of 84 kW) was supplied at a frequency of 13.56MHz employing a high frequency power source JRF-10000 produced by NipponDensi Co., Ltd. as a power source.

Optical films 31 and 32 were prepared employing a roll electrode havinga dielectric layer with an Rmax of 37 μm, and a roll electrode having adielectric layer with an Rmax of 11 μm, respectively,. wherein a 0.5W/cm² power (total power of 2.1 kW) was supplied at a frequency of 50kHz.

<<Reactive Gas>>

The composition of a mixed gas (reaction gas) used in the plasmatreatment will be shown below.

(Composition for Forming a Silicon Oxide Layer) Inert gas: argon 98.25%by volume Reactive gas 1: a hydrogen gas 1.5% by volume Reactive gas 2:tetramethoxysilane vapor 0.25% by volume (bubbled with argon gas)(Composition for forming a titanium oxide layer) Inert gas: argon 98.9%by volume Reactive gas 1: a hydrogen gas 0.8% by volume Reactive gas 2:tetraisopropoxytitanium 0.3% by volume vapor (liquid heated to 150° C.was bubbled with argon gas)

The surface b (the surface b of the film facing the stainless steel beltsupport at the dope casting) of each of film substrates 1 through 9 wassubjected to continuous atmospheric pressure plasma treatment under theabove conditions to form, on the surface b, four layers of a first highrefractive index layer (refractive index: 2.3, layer thickness: 13 nm),a first low refractive index layer (refractive index: 1.44, layerthickness: 35 nm), a second high refractive index layer (refractiveindex: 2.3, layer thickness: 122 nm), and a second low refractive indexlayer (refractive index: 1.44, layer thickness: 89 nm) in that order.

Regarding the thus obtained optical film having an anti-reflectionlayer, reflectance thereof was measured and contamination occurringduring the plasma treatment was observed.

In the optical films 22 through 30, the carbon content of each of thesilicon oxide layer and the titanium oxide layer was 1.2% by weight, andin the optical films Nos. 31 and 32, the carbon content of each of thesilicon oxide layer and the titanium oxide layer was 10.8% by weight,

<<Measurement of Reflectance (Minimum Reflectance)>>

The spectral reflectance of the resulting optical film was measuredunder condition of a 5° regular reflection through a spectrophotometerTYPE lU-4000 (produced by Hitachi Seisakusho Co., Ltd.). In order toprevent light reflection from the rear surface of the optical filmopposite the observer side, the rear surface was surface-roughened, andsubjected to light absorbing treatment employing with black spray toform a light absorbing layer. Reflectance of the resulting film wasmeasured employing a wavelength of from 400 nm through 700 nm. As aresult, inventive optical films 22 through 30 had a reflectance of lessthan 0.2, and had a flat reflection spectrum, and it was conformed thatthey had an excellent anti-reflection property. However, comparativeoptical films 31 and 32 did not sufficiently reduce reflectance. This isconsidered to result from the reduced refractive index and largevariation of the layer thickness.

(Peeling Test)

A cross cut test was carried out according to a method as described inJIS K5400. Cross cuts of 11 lines at an interval of 1 mm were formed inthe transverse and longitudinal directions through a single-edged razoron the layer surface to form one hundred grids. Then, a cellophane tapewas adhered to the cross cut surface, and the tape was sharply peeledperpendicularly. The ratio of the peeled layer area to the tape adheredarea was evaluated according to the following criteria:

-   A: No peeled layer was observed.-   B: The ratio of the peeled layer area to the tape adhered area was    less than 10%.-   C: The ratio of the peeled layer area to the tape adhered area was    not less than 10%.    <<Contamination During the Plasma Treatment>>

After the film substrate was subjected to plasma treatment,contamination in the plasma treatment chamber was observed according tothe following four criteria.

-   A: No contamination was observed.-   B: Slight contamination was observed, but not problematic.-   C: Contamination was observed to the extent that cleaning was    required.

D: Contamination was observed to the extent that troubles due to thecontamination might occur. TABLE 3 Average Peeling reflectanceContamination test Remarks Optical Film 0.2% C A Inv. film 22 substrate1 Optical Film 0.2% B A Inv. film 23 substrate 2 Optical Film 0.2% B AInv. film 24 substrate 3 Optical Film 0.2% A A Inv. film 25 substrate 4Optical Film 0.2% A A Inv. film 26 substrate 5 Optical Film 0.2% A AInv. film 27 substrate 6 Optical Film 0.2% C A Inv. film 28 substrate 7Optical Film 0.2% B A Inv. film 29 substrate 8 Optical Film 0.2% B AInv. film 30 substrate 9 Optical Film 3.5% D C Comp. film 31 substrate 2Optical Film 5.1% D C Comp. film 32 substrate 2Inv.: Invention, Comp.: Comparative

Example 3

<<Preparation of Optical Film>>

Optical films 33 through 43 were prepared employing film substrates 1through 9 described in Table 1 and employing the same plasma dischargeapparatus as in Example 1. The resulting optical films were evaluatedfor surface specific resistance, contamination occurring during theplasma treatment, and a peeling property. Details of the preparationwere described below.

In the preparation of optical films 33 through 41, the surface roughnessRmax of the dielectric layer of a roll electrode used was 5 μm, a powersource used was a high frequency power source JRF-10000 produced byNippon Densi Co., Ltd., and power of 20 W/cm² (a total power of 84 kW)was supplied at voltage with a frequency of 13.56 MHz.

The surface roughness Rmax of the dielectric layer of the roll electrodewas 37 μm in the preparation of optical film 42, and 11 μm in thepreparation of optical film 43. Power of 0.5 W/cm² (a total power of 2.1kW) was supplied at voltage with a frequency of 50 Hz in the preparationof optical films 42 and 43.

(Gas for Forming a Conductive-Layer)

-   Inert gas: argon

Reactive gas: a mixed gas of tetrabutyltin (bubbled with argon)/triethylindium (bubbled with argon)=1/1 TABLE 4 Surface specific resistancePeeling Ω/□ Contamination test Remarks Optical Film 10⁴ C A Inv. film 33substrate 1 Optical Film 10⁴ B A Inv. film 34 substrate 2 Optical Film10⁴ B A Inv. film 35 substrate 3 Optical Film 10⁴ A A Inv. film 36substrate 4 Optical Film 10⁴ A A Inv. film 37 substrate 5 Optical Film10⁴ A A Inv. film 38 substrate 6 Optical Film 10⁴ C A Inv. film 39substrate 7 Optical Film 10⁴ B A Inv. film 40 substrate 8 Optical Film10⁴ B A Inv. film 41 substrate 9 Optical Film 10⁵ D B Comp. film 42substrate 2 Optical Film 10⁷ D B Comp. film 43 substrate 2Inv.: Invention, Comp.: Comparative<<Surface Specific Resistance>>

The protective film for a polarizing plate was allowed to stand for 6hours under condition of 23° C. and 55% RH, and then the surfacespecific resistance of the surface of the film was measured under thesame condition as above, employing an insulation resistance meter (VE-30TYPE produced by Kawaguchi Denki Co., Ltd. With respect to electrodesused for measurement, two electrodes (the surface area contacting theoptical film being 1 cm×5 cm) were arranged in parallel with each otherat an interval of 1 cm. The film was brought into contact with theelectrodes and the surface specific resistance was measured. Theresulting resistance value was multiplied by five and represented interms of Ω/□ as a surface specific resistance.

Example 4

The conductive layer of each of optical films 33, 36 and 39 prepared inExample 3 was coated with coating composition (2) or (3), and furthersubjected to anti-reflection treatment, followed by formation of ananti-stain layer. Thus, optical films 44 through 49 were prepared.

<<Coating of Clear Hard Coat (CHC) Layer>>

The conductive layer of each of optical films 33, 36 and 39 above wasgravure coated with the coating composition (2) described below, driedat 80° C. in a dryer, and irradiated with UV rays at 120 mJ/cm² to givea clear hard coat layer (a center-line average surface roughness Ra of13 nm) with a dry thickness of 3 μm.

<<Anti-Glare Layer Coating>>

The conductive layer of each of optical films 33, 36 and 39 above wasgravure coated with the coating composition (3) described above, driedat 80° C. in a dryer, and irradiated with UV rays at 120 mJ/cm² to givean anti-glare layer (a center-line average surface roughness Ra of 0.25μm) with a dry thickness of 3 μm.

(Clear Hard Coat Layer (CHC Layer) Coating Composition)Dipentaerythritol hexacrylate monomer 60 parts by weightDipentaerythritol hexacrylate dimmer 20 parts by weightDipentaerythritol hexacrylate trimer 20 parts by weight or polymerhigher than the trimer Dimethoxybenzophenone 4 parts by weight(photo-initiator) Ethyl acetate 50 parts by weight Methyl ethyl ketone50 parts by weight Isopropyl alcohol 50 parts by weight

Further, a titanium oxide layer and a silicon oxide layer were formed onthe clear hard coat layer (CHC layer) or the anti-glare layer in asimilar manner as in Example 2, whereby anti-reflection treatment wascarried out. That is, the CHC layer or the anti-glare layer of each filmwas subjected to continuous atmospheric pressure plasma treatmentemploying the plasma discharge apparatus used in Example 1 to form atitanium oxide layer (with a refractive index of 2.3 and a thickness of13 nm), a silicon oxide layer (with a refractive index of 1.44 and athickness of 35 nm), a titanium oxide layer (with a refractive index of2.2 and a thickness of 122 nm), and a silicon oxide layer (with arefractive index of 1.44 and a thickness of 89 nm) on the layer in thatorder. Further, an anti-stain layer was formed on the resulting layeremploying a reactive gas for anti-stain layer formation.

(Reactive Gas for Anti-Stain Layer Formation) Inert gas: argon 99.8% byvolume Reactive gas: hexafluoropropylene 0.2% by volume

TABLE 5 Anti- Anti- reflection stain Base Film treatment layer OpticalOptical film CHC layer Present Present film 44 33 Optical Optical filmAnti-glare Present Present film 45 33 layer Optical Optical film CHClayer Present Present film 46 36 Optical Optical film Anti-glare PresentPresent film 47 36 layer Optical Optical film CHC layer Present Presentfilm 48 39 Optical Optical film Anti-glare Present Present film 49 39layer

The optical films obtained above had a uniform reflectance andfingerprints put on the films could be completely wiped off.

Example 5

A polarizing plate was prepared employing optical films 44 through 49prepared in Example 4 according to the following procedures, andevaluated.

Inventive polarizing plate 44, in which optical film 44 was used as apolarizing plate protective film, was prepared according to thefollowing procedures.

1. Preparation of Polarizing Film

A 120 μm thick long length polyvinyl alcohol film was uniaxiallystretched (at 110° C. by a factor of 5). The resulting film was immersedfor 60 seconds in an aqueous solution comprised of 0.075 g of iodine, 5g of potassium iodide, and 100 g of water, further immersed at 68° C. inan aqueous solution comprised of 6 g of potassium iodide, 7.5 g of boricacid,. and 100 g of water, washed with water, and dried. Thus, a longlength polarizing film was obtained.

2. Preparation of Polarizing Plate

The polarizing film obtained above and polarizing plate protective filmwere laminated to obtain a polarizing plate sample according to thefollowing procedures 1 to 5.

-   Procedure 1: The long length optical film. 44 prepared in Example 4    was immersed in an aqueous 2 mol/liter sodium hydroxide solution at    60° C. for 90 seconds, washed with water, and dried. A peelable    protective film (polyethylene terephthalate film) had been laminated    in advance on the anti-reflection layer of the film in order to    protect the anti-reflection layer. A long length cellulose ester    film was immersed in an aqueous 2 mol/liter sodium hydroxide    solution at 60° C. for 90 seconds, washed with water, and dried in a    similar manner as above.-   Procedure 2: The long length polarizing film obtained above was    immersed in a polyvinyl alcohol adhesive (with a solid content of 2%    by weight) for 1 to 2 seconds to form an adhesive layer.-   Procedure 3: The excessive adhesive of the adhesive layer on the    polarizing film prepared in Procedure 2 was softly removed. The    resulting polarizing film was inserted between the optical film 44    and the cellulose ester film each being alkali treated in    Procedure 1. Thus, laminate sample was obtained.-   Procedure 4: The laminate sample was passed between the two rotating    rollers at a pressure of from 20 to 30 N/cm², and at a speed of    about 2 m/min. This process was carried out carefully not to    introduce air foams in the laminate.-   Procedure 5: The sample obtained in the Procedure 4 was dried at    80° C. for 2 minutes in a dryer. Thus, inventive polarizing plate 44    was prepared.

Subsequently, polarizing plates were prepared in the same manner as inpolarizing plate 44, except that optical films 45 through 49 were usedinstead of optical film 44. Comparative polarizing plate 31 was preparedin the same manner as in polarizing plate 44, except that optical film31 was used instead of optical film 44.

The polarizing plate on the viewer side of the liquid crystal cell of acommercially available display panel (a color liquid crystal displayMultiSync LCD1525J TYPE LA-1529HM, produced by NEC Co., Ltd.) waspeeled. Subsequently, each of the polarizing plates 44 through 49 andcomparative polarizing plate 31 was adhered on the liquid crystal cellso that their polarizing direction was in accordance with the originalone. Thus, liquid crystal display panels were obtained.

The resulting liquid crystal display panels were visually observed, andas a result, the liquid crystal panels employing inventive polarizingplates provided no unevenness of reflected light, exhibiting anexcellent displaying property, as compared with the liquid crystal panel(comparative) employing comparative polarizing plate. TABLE 6 Opticalfilm Unevenness of used reflected light Polarizing Optical film Notobserved Invention plate 44 44 Polarizing Optical film Not observedInvention plate 45 45 Polarizing Optical film Not observed Inventionplate 46 46 Polarizing Optical film Not observed Invention plate 47 47Polarizing Optical film Not observed Invention plate 48 48 PolarizingOptical film Not observed Invention plate 49 49 Polarizing Optical filmApparently observed Comparative plate 31 31

Example 6

In the optical film 90 prepared by coating a TiO₂ layer with a thicknessof 100 nm on film substrate 8 employing a vacuum coater LOAD-LOCK TYPEVACUUM ROLL COATER EWA-310 produced by Nippon Sinku Co., Ltd., andoptical films 8A, 8C, 8D, 8F and 8N prepared in Example 1, the carboncontent of the formed layer was measured according to the methoddescribed below. Further, these optical films were evaluated for ananti-abrasion property.

<<Measurement of Carbon Content>>

The carbon content was measured employing an XPS surface analyzer. TheXPS surface analyzer used is not specifically limited, and any kinds ofsurface analyzers can be used, but in the examples, ESCALAB-200Rproduced by VG Scientifics Co., Ltd. was employed. Measurement was madeat an output of 600 W (an acceleration voltage of 15 kV, and emissioncurrent of 40 mA), employing Mg as an X ray anode. Energy dissolutionregulated to a peak width at half height of clean Ag 3d5/2 was set to be1.5 to 1.7 eV. In order to eliminate an influence due to contamination,it is necessary that before measurement, a surface layer correspondingto 10 to 20% of the formed layer thickness be removed by etching. Thesurface layer is preferably removed employing an ion gun capable ofusing a rare gas ion. Examples of the ion include an ion of He, Ne, Ar,Xe, or Kr. In this example, the surface layer was removed employingargon ion etching.

Measurement was made at a measurement interval of 1.0 eV in the bondenergy range of 0 to 1100 eV, and firstly, an element to be detected wasexamined. Next, measurement was made at a measurement interval of 0.2 eVon each of the detected elements except for the element for etching, anda narrow scanning of the photo-electron peak providing a maximumintensity was carried out. Thus, the spectrum of each element wasobtained. In order to eliminate variation of the carbon content obtaineddue to kinds of analyzers or computers employed, the resulting spectrumwas transferred to COMMON DATA PROCESSING SYSTEM (preferably Version 2.3or Versions thereafter) produced by VAMAS-SCA-JAPAN Co., Ltd., andprocessed with its software to obtain a carbon content in terms ofatomic concentration.

Before quantitative processing, calibration of Count Scale on eachelement detected was carried out, and 5 point smoothing processing wascarried out. In the quantitative processing, the peak area intensity(cps-eV) except for the background was employed. The backgroundprocessing was carried out employing a Shirley method. The Shirleymethod was described in D. A. Shirley, Phys. Rev., BS, 4709 (1972).<Measurement of anti-abrasion property>

A 1×1 cm² probe to which a steel wool was adhered was put on the layerof the optical films, loaded with a 250 g load, and reciprocated 10times. The number of abrasion lines was counted. TABLE 7 Carbon Anti-Optical content abrasion film Coating method weight % property RemarksOptical Atmospheric 5 1 Invention film 8A pressure plasma OpticalAtmospheric 3 0 Invention film 8C pressure plasma Optical Atmospheric0.3 0 Invention film 8D pressure plasma Optical Atmospheric 0.2 1Invention film 8F pressure plasma Optical Atmospheric 23 34 Comparativefilm 8I pressure plasma Optical Atmospheric 7 21 Comparative film 8Npressure plasma Optical Vacuum Not 27 Comparative film 90 depositiondetected

Example 7

<<Preparation of Optical Film>>

Optical films 50 through 55 were prepared employing film substrate 8 asshown in Table 1 and the plasma discharge apparatus used in Example 1,except that inventive dielectric coated electrode set B was replacedwith the inventive dielectric coated electrode set A, and the dischargesurface area, power supplied, and voltage applying method were as shownin Table 8.

Details of the Preparation will be Described Below.

In the above preparation, the discharge surface area was adjusted bychanging the length in the transverse direction of the electrodes to 100cm (the width of film substrate was also changed), and varying thelength in the transport direction of the prismatic electrodes and thenumber used thereof.

<<Voltage Applying Method>>

Continuous sine-shaped wave: frequency of 13.56 MHz

<<Reactive Gas>>

The composition of a mixed gas (reactive gas) used in the plasmatreatment is shown below.

(Composition for Forming Titanium Oxide Layer) Inert gas: argon 98.8% byvolume Reactive gas 1: a hydrogen gas 1.0% by volume Reactive gas 2:tetraisopropoxytitanium vapor 0.2% by volume (liquid heated to 150° C.was bubbled with argon gas)

The surface b of film substrate 8 (the surface of the film facing thestainless steel belt support at the dope casting) was subjected toatmospheric pressure plasma treatment under the above conditions to forma layer (with a refractive index of 2.3 and a thickness of 100 nm)containing a titanium oxide as a main component. The thus obtainedoptical films were evaluated for layer thickness deviation andrefractive index distribution. The results are shown in Table 8.

<Evaluation of Layer Thickness Deviation>

The layer thickness was measured according to the thickness measuringmethod as carried out in Example 1. The layer thicknesses were measuredat 99 points at an interval of 1 cm between a length of 100 cm in thetransverse direction of the optical film, and the layer thicknessdeviation was obtained from the resulting layer thicknesses.${{Layer}\quad{thickness}\quad{deviation}} = \frac{{{Measuring}\quad{{number} \cdot {\Sigma({Thickness})}^{2}}} - \left( {\Sigma({Thickness})}^{2} \right)}{{Measuring}\quad{{number} \cdot \left( {{{Measuring}\quad{number}} - 1} \right)}}$<Evaluation of Refractive Index Distribution>

The refractive index was measured according to the refractive indexmeasuring method as carried out in Example 1. The refractive indexeswere measured at 99 points at an interval of 1 cm between a length of100 cm in the transverse direction of the optical film, and therefractive index distribution was obtained from the resulting refractiveindexes.${{Refractive}\quad{index}\quad{distribution}} = \frac{{{Measuring}\quad{{number} \cdot {\Sigma\left( {{refractive}\quad{index}} \right)}^{2}}} - \left( {\Sigma\left( {{refractive}\quad{index}} \right)}^{2} \right)}{{Measuring}\quad{{number} \cdot \left( {{{Measuring}\quad{number}} - 1} \right)}}$TABLE 8 Length in Length the transport in the direction of transportdischarge surface/ direction of Length in Discharge Layer discharge thetransverse surface Output Total thickness Refractive Sample surfacedirection of area density power deviation index No. (cm) dischargesurface cm² W/cm² supplied % distribution 50 5 1/20 500 15 7.5 kW  ±3.52.21 ± 0.11 51 8 2/25 800 15 12 kW ±3.0 2.23 ± 0.11 52 10 1/10 1000 1515 kW ±1.0 2.24 ± 0.10 53 20 ⅕  2000 15 30 kW ±0.8 2.28 ± 0.03 54 50 ½ 5000 15 75 kW ±0.5 2.30 ± 0.02 55 100 1/1  10000 15 150 kW  ±0.4 2.32 ±0.02

The total power exceeding 15 kW can provide excellent refractive indexdistribution. Further, it has been proved that when length in thetransport direction of discharge surface/length in the transverse ofdischarge surface of not less than 1/10, the layer thickness deviationis reduced, which provides a uniform layer thickness.

INDUSTRIAL APPLICATION

The present invention provides an electrode system le of resisting highvoltage and high output, can carry stable discharge treatment capable ofresisting production over a long time, and can provide a uniform layerwith high performance at a high speed.

1-60. (canceled)
 61. A dielectric coated electrode, comprising aconductive base material, and a dielectric layer which comprises, aceramic layer and a sealing material, wherein the dielectric layercovers the conductive base material and has a void volume of not morethan 10% and a maximum surface roughness Rmax of not more than 10 μm;and the dielectric coated electrode is prismatic.
 62. (canceled)
 63. Thedielectric coated electrode of claim 61, wherein the electrode has aheat resistant temperature of not less than 100° C.
 64. The dielectriccoated electrode of claim 61, wherein the difference in a linear thermalexpansion coefficient between the conductive base material and thedielectric layer in the dielectric coated electrode is not more than10×10⁻⁶/° C.
 65. The dielectric coated electrode of claim 61, whereinthe dielectric layer has a thickness of from 0.5 to 2 mm.
 66. Thedielectric coated electrode of claim 61, wherein the dielectric is aninorganic compound having a dielectric constant of from 6 to
 45. 67.(canceled)
 68. The dielectric coated electrode of claim 61, wherein theceramic comprises alumina as a main component.
 69. The dielectric coatedelectrode of claim 61, wherein the sealing material is an inorganiccompound and the inorganic compound is hardened by a sol-gel reaction.70. The dielectric coated electrode of claim 69, wherein the sol-gelreaction is accelerated by energy treatment.
 71. The dielectric coatedelectrode of claim 70, wherein the energy treatment is heat treatment atnot more than 200° C. or UV radiation treatment.
 72. The dielectriccoated electrode of claim 69, wherein the inorganic compound for thesealing after the sol-gel reaction contains not less than 60 mol % ofSiO_(x).
 73. The dielectric coated electrode of claim 61, wherein thesurface of the dielectric layer is surface finished by polishingtreatment.
 74. (canceled)
 75. The dielectric coated electrode of claim61, wherein the electrode has a cooling means comprising a path forchilled water in the interior of the conductive base material, theelectrode being cooled by supplying chilled water to the path. 76.(canceled)
 77. A plasma discharge apparatus comprising: a firstelectrode and a second electrode opposed to each other, a gas supplierto supply a reactive gas, and a power source to apply voltage across thefirst electrode and the second electrode at atmospheric pressure orapproximately atmospheric pressure to induce a discharge, the reactivegas supplied by the gas supplier being changed into a reactive gas in aplasma state by the discharge and then a layer being formed by exposinga substrate to the reactive gas in a plasma state, wherein at least oneof the first electrode and second electrode is a dielectric coatedelectrode which comprises a conductive base material and a dielectriclayer which covers the conductive base material; the dielectric layerhaving a void volume of not more than 10% and a maximum surfaceroughness Rmax of not more than 10 μm. 78-86. (canceled)
 87. Thedielectric coated electrode of claim 61, wherein the sealing employs aninorganic compound.
 88. The dielectric coated electrode of claim 61,wherein the dielectric layer has the maximum surface roughness Rmax ofnot more than 8 μm.
 89. The dielectric coated electrode of claim 88,wherein the dielectric layer has the maximum surface roughness Rmax ofnot more than 7 μm.
 90. The dielectric coated electrode of claim 61,wherein the dielectric layer has a centerline average surface roughnessRa of not more than 0.5 μm.
 91. The dielectric coated electrode of claim90, wherein the dielectric layer has the centerline average surfaceroughness Ra of not more than 0.1 μm.
 92. The dielectric coatedelectrode of claim 61, wherein the dielectric layer has the void volumeof not more than 8%.